Side Dishes
This baked cod with potatoes and onions recipe delivers a restaurant-worthy meal with minimal effort—crispy golden skin on the fish, flaky white flesh, and perfectly caramelized onions that melt into every bite.
The secret lies in a single pan where everything cooks together, creating a harmonious balance of textures and flavors that feels both comforting and refined. I developed this recipe after years of testing one-pan seafood dishes, and it never fails to impress, even with the simplest ingredients.
The beauty of this dish is its simplicity: no fancy techniques, no last-minute shopping trips. You'll start with fresh cod fillets, baby potatoes cut into even pieces, and sweet onions that caramelize beautifully in the oven.
A light brushing of olive oil and a sprinkle of herbs ensure the cod stays moist while developing that coveted crispy top. The potatoes absorb the flavors of the onions and fish, creating a cohesive dish where every component complements the others.
What you'll end up with is a plate that looks as good as it tastes—golden, aromatic, and inviting. The cod flakes easily at the touch of a fork, the potatoes are tender with crisp edges, and the onions have softened into a sweet, caramelized blanket that ties everything together.
This is the kind of meal that transforms a casual weeknight dinner into something special, without requiring hours in the kitchen or advanced skills.
Serve it with a squeeze of lemon and a sprinkle of fresh parsley for brightness, or pair it with a simple green salad to balance the richness. The leftovers reheat beautifully, making this an ideal recipe for meal prep or feeding a crowd.
Let’s get started on creating this one-pan masterpiece that’s as foolproof as it is delicious.
Ingredients for baked cod with potatoes and onions
Fresh cod, tender potatoes, and sweet onions create a restaurant-quality meal with minimal prep work.
| Ingredient | Amount | Notes |
|---|---|---|
| Cod Fillets 🐟 | 2 whole | Skin-on, center-cut preferred |
| Baby Potatoes 🥔 | 1 ½ lb | Halved, unpeeled for texture |
| Sweet Onions 🧅 | 2 whole | Yellow or Vidalia, sliced thin |
| Extra-Virgin Olive Oil 🫒 | ¼ cup | High-quality, fruity variety |
| Fresh Lemon 🍋 | 1 whole | Juiced for brightness |
| Fresh Dill 🌿 | ¼ cup | Chopped, stems removed |
| Fresh Parsley 🌿 | ¼ cup | Chopped for garnish |
| Garlic Cloves 🧄 | 3 cloves | Minced for seasoning |
| Salt 🧂 | 1 ½ tsp | Kosher or sea salt |
| Ground Black Pepper 🌶️ | ½ tsp | Freshly ground preferred |
| Paprika 🌶️ | ½ tsp | Smoked for color |
| Dried Thyme 🌿 | ½ tsp | Or 1 tbsp fresh thyme |
The cod is the star here, so look for center-cut fillets with skin—it crisps beautifully while keeping the flesh moist. Whole Foods or local fish markets often carry the freshest cod, but don't overlook your grocery store's seafood counter if it's well-stocked. For onions, Vidalia or yellow sweet onions caramelize best without turning bitter. Baby potatoes should be uniform in size so they cook evenly. If you can't find baby potatoes, cut larger Yukon Golds into even halves—they hold their shape better than red potatoes.
No fresh dill? Fresh parsley at double the amount works in a pinch, though it lacks the bright anise notes. Running short on thyme? Oregano at half the quantity mimics its earthy depth. The lemon juice is non-negotiable for brightness—bottled lemon juice lacks the complexity, so squeeze fresh if possible. For the olive oil, avoid light or refined oils—they lack the fruity depth that enhances the cod's natural flavor. If you're short on time, pre-sliced onions from the refrigerated section save chopping, though fresh-cut onions caramelize more beautifully.
This dish reheats beautifully—cover with foil and warm in a 350°F oven for 10 minutes. Store leftovers in an airtight container for up to 3 days, but the cod is best consumed within 2 days. For meal prep, portion the potatoes and onions separately—they hold up better individually. The cod's skin crisps best when eaten fresh, but the potatoes and onions can be prepped ahead and stored in the fridge for 2 days before baking.
Why You'll Love This Recipe
- One-Pan Magic: I swear by this for lazy nights—just toss everything on a sheet pan, drizzle with olive oil, and let the oven do the work. No chopping boards, no extra pots, just golden, flaky cod and caramelized onions all in one go.
- Zesty, Crispy, Creamy: That lemon zest on the cod? Bright, tangy perfection. The potatoes get tender and crispy at the edges, while the onions melt into sweet, jammy perfection. Honestly, the flavor balance is chef’s kiss—simple but impossible to resist.
- Weeknight to Weekend: Between us, this feeds a crowd without stress. Double the cod for dinner guests, or prep the potatoes ahead and roast fresh when company arrives. Even my picky teenager asks for seconds—high praise, indeed.
- Leftovers That Don’t Suck: Unlike fish that turns rubbery, this stays moist for days. Reheat gently, and it’s just as good the next lunch—perfect for meal prep. Plus, cod’s budget-friendly, so you’re saving money without sacrificing taste. Win-win.
Step-by-step instructions for baked cod with potatoes and onions
Here's how to achieve perfectly crispy potatoes and flaky cod in one elegant pan.
Prep the Vegetables and Season the Cod
Preheat your oven to 425°F while you prepare the vegetables. Halve the 1.5 lb baby potatoes lengthwise, leaving the skins on for texture. Thinly slice the 2 whole sweet onions into even rounds - about ⅛-inch thick. This even slicing ensures they cook through without burning.
Pat the 2 whole cod fillets completely dry with paper towels - moisture is the enemy of crispy skin. In a small bowl, mix 1.5 tsp salt, 0.5 tsp ground black pepper, 0.5 tsp paprika, and 0.5 tsp dried thyme. Rub this seasoning generously over both sides of each fillet, pressing it into the flesh. The paprika will give you that beautiful golden crust while the thyme adds depth.
Layer the Potatoes and Onions
In a large oven-safe skillet with a lid, arrange the halved potatoes in a single layer, cut-side down. This creates a stable base that won't shift during baking. Pour 0.25 cup extra-virgin olive oil evenly over the potatoes, then sprinkle with half of the minced 3 cloves garlic. Toss gently to coat.
Add the sliced onions in an even layer over the potatoes. The onions should nestle between the potato halves. Drizzle with half of the freshly squeezed juice from the 1 whole fresh lemon (about 2 tablespoons). The acidity will tenderize the onions while balancing the richness of the cod. Don't skip this step - it makes all the difference in flavor.
Arrange the Cod and Bake
Place the seasoned cod fillets on top of the onion layer, skin-side up. The cod should sit flat against the onions without crowding. If needed, gently press down to create contact points. This ensures even cooking and maximum crispiness. Drizzle the remaining lemon juice over the cod and sprinkle with the remaining minced garlic.
Cover the skillet tightly with foil and bake for 20 minutes. This initial covered baking steams the vegetables slightly, preventing them from drying out while the cod begins to cook gently. After 20 minutes, remove the foil and bake uncovered for an additional 12-15 minutes until the potatoes are golden brown and the cod flakes easily with a fork.
Finish with Fresh Herbs and Serve
When the cod is done, it should have a crispy golden crust on top and be just opaque in the center - the flesh should separate cleanly with a fork. Remove the skillet from the oven and let it rest for 3-4 minutes before serving. This resting period allows the juices to redistribute in the cod.
Before serving, sprinkle the dish generously with the chopped 0.25 cup fresh dill and 0.25 cup fresh parsley. The fresh herbs add a bright finish that cuts through the richness of the cod and potatoes. Serve immediately with the pan juices spooned over the top - these contain all the concentrated flavors from the baking process.
Pro Tips For Making Baked Cod With Potatoes And Onions
- Pare the Potatoes: I learned this the hard way—halving baby potatoes without paring them first means uneven cooking and a gummy center. Use a peeler to shave off just the toughest outer layer (no need to go deep), then quarter any larger ones. This ensures they crisp up faster while staying tender inside.
- Salt the Cod First: Skip the "season after baking" habit—pat the cod dry, then sprinkle it with salt and let it sit for 10 minutes before adding oil. This step guarantees the seasoning penetrates instead of just sitting on the surface, and the fillets hold up better when you flip them.
- Layer Onions Like a Roast: Don’t just toss sliced onions into the pan—they’ll steam and turn mushy. Instead, arrange them in a single overlapping layer under the potatoes, cut-side down. This creates a crispy, caramelized base that actually holds the dish together, and they cook evenly without falling apart.
- Bake in Two Stages: Your oven’s broiler is your friend here. Roast the potatoes and onions at 400°F (200°C) for 20 minutes first, then crank the broiler to 500°F (260°C) for the last 5 minutes. The high heat at the end gets that golden crust on the cod without drying it out—just watch it like a hawk to avoid burning.
Creative variations of baked cod with potatoes and onions
Mediterranean Herb Twist
Swap out the dill for 1 tbsp dried oregano and 1 tbsp dried rosemary to transform this dish into a Mediterranean-inspired masterpiece. Add ½ cup cherry tomatoes, halved, to the onion layer before baking.
The tomatoes will burst and caramelize, adding a sweet-tart contrast. Finish with ¼ cup crumbled feta cheese and a drizzle of high-quality extra-virgin olive oil before serving for that signature Greek flair. 🌿
Spicy Cajun Cod
For a bold kick, mix 1 tbsp Cajun seasoning (like Tony Chachere's) with the paprika and thyme when seasoning the cod. Add ½ cup sliced bell peppers (any color) with the onions for a colorful twist.
Serve with a side of cornbread and a squeeze of hot sauce for dipping. The Cajun spices will give the cod a smoky, spicy crust that pairs perfectly with the sweet potatoes. 🌶️
Garlic Butter Potatoes
Elevate the potatoes by adding 4 tbsp melted butter to the olive oil before tossing with the potatoes and onions. Mix in 1 tbsp minced garlic and 1 tsp garlic powder for an extra-rich, garlicky depth.
After baking, spoon the buttery pan juices over the cod before serving. This upgrade turns the potatoes into a decadent side that rivals the star of the show. 🧄
Lemon-Dill Sauce
Transform leftovers or serve alongside the main dish with a bright lemon-dill sauce. Whisk together ½ cup Greek yogurt, 2 tbsp lemon juice, 2 tbsp chopped fresh dill, 1 tbsp chopped parsley, 1 tsp honey, and ½ tsp salt.
Drizzle this creamy sauce over the baked cod and potatoes for a restaurant-quality finish. The sauce cuts through the richness and adds a refreshing tang. 🍋
Herb-Infused Oil Drizzle
Create a fragrant finishing touch by infusing ¼ cup olive oil with 1 tbsp fresh thyme, 1 tbsp fresh rosemary, and 2 garlic cloves. Heat the oil gently for 5 minutes to release the flavors, then strain and drizzle over the finished dish.
This aromatic oil enhances every bite with a herbal, garlicky depth that ties all the components together beautifully. ✨
Nutrition facts
Frequently asked questions
Can I use frozen cod instead of fresh?
Yes, but thaw it properly first! Place the frozen cod in the refrigerator overnight (about 12-24 hours) or use the quick thaw method in cold water. Never thaw at room temperature, as this can promote bacterial growth. Pat the cod completely dry before seasoning to ensure crispy skin. Frozen cod works just as well but may release more water during baking.
What if my potatoes turn mushy instead of crispy?
This usually happens from overcrowding or too much moisture. Halve the baking time by 5-7 minutes and check for doneness early. Also ensure your potatoes are cut evenly and arranged in a single layer. If using waxy potatoes, reduce the baking time by 2-3 minutes—they cook faster than baby potatoes. For extra crispiness, broil for 1-2 minutes at the end.
How do I know when the cod is fully cooked?
The cod is done when it reaches an internal temperature of 145°F and flakes easily with a fork. Look for opaque, milky-white flesh that separates cleanly at the thickest part. The skin should be golden and crispy. If unsure, cut into the thickest part—it should look fully cooked through without any translucent areas. Overcooking can make the fish dry, so aim for 12-15 minutes uncovered.
Can I make this ahead of time for a meal prep?
Yes! Prep the potatoes and onions 1 day ahead and store them in the fridge. Assemble the dish in the skillet and refrigerate uncovered for up to 12 hours before baking. When ready to cook, bake at 425°F for 25-30 minutes (covered for 15 minutes, then uncovered). The cod is best eaten fresh, but the potatoes and onions reheat beautifully. Store leftovers in an airtight container for 2 days.
What’s the best way to reheat leftovers?
Reheat gently to avoid drying out the cod. Cover the skillet with foil and warm in a 350°F oven for 10 minutes. For a crispier texture, broil for 1-2 minutes at the end. Alternatively, reheat in a microwave for 1-2 minutes on medium power, then cover with a damp paper towel to retain moisture. Avoid reheating cod more than once, as it can become tough.