Roast Salmon With Leeks and Onions

Featured in: Quick Weeknight Dinners

This one-pan salmon dish combines tender roasted fish with caramelized leeks and red onions, all brought together with a bright parsley dressing. The entire meal comes together in just 40 minutes with minimal cleanup—perfect for busy weeknights. The vibrant parsley dressing, made with garlic, capers, and lemon, adds a fresh, zesty finish that elevates the rich salmon and sweet roasted vegetables.

Updated on Thu, 29 Jan 2026 10:38:00 GMT
Golden-brown roasted leeks and red onions surround tender, flaky skin-on salmon fillets, garnished with fresh parsley dressing. Save
Golden-brown roasted leeks and red onions surround tender, flaky skin-on salmon fillets, garnished with fresh parsley dressing. | whisknjoy.com

There's something wonderfully honest about a one-pan dinner that asks nothing of you except patience and a hot oven. I discovered this salmon setup on a Tuesday night when I had exactly forty minutes, three hungry people coming over, and zero energy for fussing. The magic happened when I realized that roasting salmon alongside sweet caramelized leeks and onions meant everything cooked in its own time, at its own pace, while I stood there sipping coffee and watching it all come together.

I made this for my sister on her first night back from traveling, when she walked into the kitchen and the smell of roasting leeks and salmon hit her all at once. She actually paused mid-sentence and just breathed in. That's when I knew this wasn't just efficient dinner—it was the kind of meal that tastes like someone cared enough to get the flavors right.

Ingredients

  • Salmon fillets (4, skin-on, about 150g each): Skin-on matters because it crisps slightly at the edges and keeps the flesh from drying out; buy from a fishmonger if you can, and ask them to check for bones.
  • Leeks (2 large, trimmed and sliced into 1/2-inch rounds): The white and light green parts are the stars here, sweet and almost buttery once roasted; slice them carefully so they stay in rings.
  • Red onion (1 large, sliced into wedges): The mild tartness balances the richness of the salmon beautifully.
  • Olive oil (2 tbsp for roasting, plus 3 tbsp extra-virgin for dressing): Use regular olive oil for roasting since it handles heat better, then splurge on good extra-virgin for the dressing where you'll actually taste it.
  • Sea salt and black pepper: Season in layers—on the vegetables first, then taste the salmon at the end.
  • Lemon (1, sliced for the pan, plus juice and zest for the dressing): Fresh lemon is non-negotiable here; it brightens everything and cuts through the richness.
  • Fresh flat-leaf parsley (1 cup, finely chopped): Use a sharp knife or your hands to chop it fine; the texture matters more than you'd think.
  • Garlic clove (1 small, minced): Just a whisper of garlic keeps the dressing from being one-note.
  • Dijon mustard (1/2 tsp): A small amount acts as an emulsifier and adds subtle depth.
  • Capers (1 tsp, drained and chopped): Those briny little bursts are what make people ask what that flavor is.
  • Lemon zest (1/2 tsp): Zest before you juice; your hands will thank you.
  • Fresh lemon juice (1 tbsp): Bottled works in a pinch, but fresh makes an actual difference in a dressing this simple.

Instructions

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Heat your oven and prepare the pan:
Preheat to 400°F and grab your largest baking sheet—you want room for everything to spread out without crowding. A crowded pan steams instead of roasts, and we're after that golden, tender caramelization.
Get the vegetables going:
Scatter your leek rounds and onion wedges across the sheet, drizzle with olive oil, season with salt and pepper, and toss until everything's coated. Roast for 10 minutes alone so they start to soften and the edges begin to catch and brown.
Add the salmon:
Pull the sheet out carefully and nestle your salmon fillets skin-side down among the vegetables—the heat from the pan will crisp that skin beautifully. Lay lemon slices right over the top and return everything to the oven.
Let it finish:
Roast for 12 to 15 minutes until the salmon flakes easily with a fork and the vegetables are completely tender. You're looking for the fish to be just cooked through, not dry—the residual heat will keep cooking it even after you pull it out.
Make the dressing while everything roasts:
In a small bowl, combine your chopped parsley, minced garlic, mustard, capers, and lemon zest. Stir in the extra-virgin olive oil and lemon juice, then taste and adjust salt and pepper—this dressing should be bright and confident.
Plate and serve:
Transfer salmon and vegetables to plates, spoon that verdant dressing generously over the top, and serve right away while everything's still warm and the flavors are singing.
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Bright One-Pan Roast Salmon with Leeks, Onions, and Parsley Dressing served on a plate with lemon wedges. Save
Bright One-Pan Roast Salmon with Leeks, Onions, and Parsley Dressing served on a plate with lemon wedges. | whisknjoy.com

My neighbor once asked why I wasn't serving this at a dinner party, and I realized it's because it looks too easy—almost suspiciously so. But that's the beauty of it; the simplicity is the whole point, and somehow that makes people slow down and actually taste what they're eating instead of rushing through something complicated.

The Secret to Crispy Salmon Skin

Pat your salmon fillets completely dry with paper towels before they hit the pan; any moisture on the skin will turn it steamy instead of crispy. Place them skin-side down directly on the hot sheet and resist the urge to move them around—let them sit undisturbed so that skin makes real contact with the heat.

Variations and Swaps

Trout or cod work beautifully here if salmon isn't what you're after, though they're more delicate so watch your timing carefully. You can swap the red onion for shallots if you want something milder, or add thin fennel slices alongside the leeks for an almost anise-like note. The parsley dressing is flexible too—try fresh dill or basil if you have it, or add a pinch of crushed red pepper flakes if you want to wake things up.

Making It a Proper Meal

This dish sings on its own, but if you want something more substantial, roasted potatoes tossed with a little olive oil and sea salt are your friend—they can roast on a separate sheet at the same temperature while you're working. Steamed rice is gentler and lets the salmon be the star, while a simple green salad adds freshness and cuts through the richness beautifully.

  • Roast crushed fingerling potatoes alongside everything for a more complete meal.
  • Serve with a chilled white wine like a Sauvignon Blanc that has enough acidity to match the lemon dressing.
  • Make extra parsley dressing and keep it in the fridge for drizzling over leftovers the next day.
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Sizzling One-Pan Roast Salmon with Leeks, Onions, and Parsley Dressing fresh from the oven on a rustic baking sheet. Save
Sizzling One-Pan Roast Salmon with Leeks, Onions, and Parsley Dressing fresh from the oven on a rustic baking sheet. | whisknjoy.com

This meal has become my answer to the question of what to make when you want something that feels thoughtful but doesn't demand that you spend your whole evening in the kitchen. It's the kind of dinner that leaves you with actual time to sit and talk instead of rushing between the stove and the table.

Recipe FAQ

Can I use frozen salmon fillets?

Yes, just ensure they are fully thawed and patted dry before roasting to achieve the best texture and proper cooking.

What can I substitute for leeks?

You can use sliced fennel, shallots, or additional red onions. Each will bring a slightly different flavor profile to the dish.

How do I know when the salmon is cooked through?

The salmon should flake easily with a fork and reach an internal temperature of 145°F. The flesh will appear opaque throughout.

Can I make the parsley dressing ahead of time?

Yes, prepare it up to 2 hours ahead and store covered at room temperature. Give it a quick stir before serving.

What sides pair well with this dish?

Roasted potatoes, steamed rice, quinoa, or crusty bread complement the salmon beautifully. A simple green salad also works well.

Can I use dried parsley instead of fresh?

Fresh parsley is strongly recommended for the dressing as it provides the bright, herbaceous flavor that defines this dish. Dried parsley won't deliver the same vibrant taste.

Roast Salmon With Leeks and Onions

Roasted salmon with leeks, onions, and vibrant parsley dressing. Gluten-free, ready in 40 minutes.

Prep duration
15 min
Cook duration
25 min
Complete duration
40 min
Created by Sophia Turner

Classification Quick Weeknight Dinners

Skill Level Easy

Cultural Background Modern European

Output 4 Portion Count

Dietary considerations No Dairy, No Gluten, Low-Carbohydrate

Components

Fish & Vegetables

01 4 salmon fillets (about 5.3 oz each), skin-on
02 2 large leeks, trimmed and sliced into 1/2-inch rounds
03 1 large red onion, sliced into wedges
04 2 tablespoons olive oil
05 1/2 teaspoon sea salt
06 1/4 teaspoon black pepper
07 1 lemon, sliced

Parsley Dressing

01 1 cup fresh flat-leaf parsley, finely chopped
02 1 small garlic clove, minced
03 1/2 teaspoon Dijon mustard
04 1 teaspoon capers, drained and chopped
05 1/2 teaspoon lemon zest
06 3 tablespoons extra-virgin olive oil
07 1 tablespoon fresh lemon juice
08 Salt and pepper, to taste

Preparation Steps

Stage 01

Preheat oven: Preheat the oven to 400°F.

Stage 02

Prepare vegetables: Arrange the leeks and red onion in a single layer on a large baking sheet. Drizzle with olive oil, sprinkle with salt and pepper, and toss to coat evenly.

Stage 03

Initial vegetable roast: Roast the vegetables for 10 minutes until they begin to soften.

Stage 04

Add salmon: Remove the baking sheet from the oven. Nestle the salmon fillets skin-side down among the vegetables. Arrange lemon slices over the salmon.

Stage 05

Complete roasting: Return to the oven and roast for 12-15 minutes, or until the salmon is just cooked through and vegetables are tender.

Stage 06

Prepare parsley dressing: While the salmon bakes, combine parsley, garlic, Dijon mustard, capers, lemon zest, olive oil, and lemon juice in a small bowl. Stir well and season with salt and pepper to taste.

Stage 07

Plate and serve: Transfer the roasted salmon and vegetables to plates. Spoon the parsley dressing generously over the salmon and serve immediately.

Necessary tools

  • Large baking sheet
  • Sharp knife
  • Mixing bowls
  • Spoon or whisk

Allergy details

Review all ingredients for potential allergens and consult with healthcare professionals if you're unsure about any item.
  • Contains fish (salmon)
  • Contains mustard

Nutritional content (each portion)

These values are provided as estimates only and shouldn't replace professional medical guidance.
  • Energy: 365
  • Fats: 23 g
  • Carbohydrates: 10 g
  • Proteins: 30 g