Roast Salmon With Leeks Onions

Featured in: Garden-Inspired Meals

This one-pan roasted salmon delivers maximum flavor with minimal effort. Tender salmon fillets nestle among caramelized leeks and red onions, all roasted together for easy preparation and cleanup. The dish is elevated with a vibrant parsley dressing featuring garlic, capers, lemon zest, and Dijon mustard that adds brightness and depth. Perfect for busy weeknights, this gluten-free and dairy-free meal is ready in just 40 minutes and serves four.

Updated on Thu, 29 Jan 2026 12:36:00 GMT
Golden-brown One-Pan Roast Salmon fillets nestled among tender roasted leeks and onions, topped with a vibrant green parsley dressing. Pin
Golden-brown One-Pan Roast Salmon fillets nestled among tender roasted leeks and onions, topped with a vibrant green parsley dressing. | toastybasil.com

There's something about the sound of a baking sheet sliding into a hot oven that makes me feel like I've got dinner under control, and this one-pan salmon situation is exactly that kind of magic. My neighbor once stopped by mid-cook and the aroma of caramelizing leeks mixed with roasting salmon made her pause at the kitchen door—that's when I knew this was worth repeating. The whole thing comes together in under 40 minutes, which means you're not standing around exhausted when it's time to eat. The parsley dressing is the secret move that transforms something simple into something guests actually ask for the recipe to.

I made this for a friend who'd been on a restrictive diet, and watching her face when she tasted the combination of buttery salmon with those soft, sweet roasted leeks was surprisingly emotional. She'd been eating plain grilled proteins for weeks, and suddenly she was back in the world where food could be both good for you and genuinely delicious. That moment taught me that simple doesn't mean boring, especially when you pick your ingredients with intention.

Ingredients

  • Salmon fillets (4, about 150g each), skin-on: The skin keeps the fish moist and gets wonderfully crispy in the oven, so please don't skip it—this is where the textural magic happens.
  • Leeks (2 large, sliced into 1/2-inch rounds): Leeks mellow out when roasted and develop this subtle sweetness that plays beautifully with the salmon, but make sure you clean them thoroughly between layers.
  • Red onion (1 large, sliced into wedges): The sharper bite of red onion balances the richness of the fish and adds a pop of color that makes the plate feel alive.
  • Olive oil (2 tbsp for roasting, 3 tbsp extra-virgin for dressing): Use regular olive oil for roasting since high heat breaks down the delicate flavor of extra-virgin, then save the good stuff for the dressing where you'll actually taste it.
  • Sea salt and black pepper: Taste as you season the vegetables, because they'll release moisture and concentrate flavors as they roast.
  • Lemon (1, sliced): Fresh lemon slices on top of the salmon infuse moisture and brightness as everything cooks together.
  • Fresh flat-leaf parsley (1 cup, finely chopped): This is your star ingredient for the dressing—curly parsley won't give you the same clean, herbaceous punch, so don't substitute.
  • Garlic clove (1 small, minced): One clove is enough; mince it fine so it dissolves into the dressing rather than creating little surprises.
  • Dijon mustard (1/2 tsp): This tiny amount emulsifies the dressing and adds a subtle tang that ties everything together without overpowering.
  • Capers (1 tsp, drained and chopped): Their salty brine adds complexity and a briny pop that makes people wonder what you did to make it taste restaurant-quality.
  • Lemon zest (1/2 tsp): Use a microplane or the smallest holes on your box grater so the zest disperses evenly through the dressing.
  • Fresh lemon juice (1 tbsp): Squeeze it fresh right before mixing; bottled juice tastes flat by comparison.

Instructions

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Heat your oven and prep your pan:
Preheat to 400°F (200°C) and line a large baking sheet with parchment paper if you want the easiest cleanup of your life. While the oven comes to temperature, slice your leeks and onion so everything's ready to go.
Get the vegetables started:
Toss the leeks and red onion with 2 tablespoons of olive oil, a pinch of salt, and pepper, then spread them in a single layer on your baking sheet. Roast for 10 minutes so they start to soften and the edges begin to caramelize.
Nestle in the salmon:
Pull the sheet out carefully and arrange your salmon fillets skin-side down among the vegetables, then lay lemon slices right on top of each fillet. Return to the oven for 12 to 15 minutes—the salmon will go from translucent to opaque, and that's your signal to pull it out.
Make the dressing while everything cooks:
In a small bowl, combine the parsley, garlic, mustard, capers, and lemon zest, then stir in the extra-virgin olive oil and fresh lemon juice. Season with salt and pepper to taste, and give it a final stir so everything's evenly distributed.
Plate and serve:
Transfer the salmon and roasted vegetables to plates with a little care so the fillets stay intact, then spoon that bright green dressing generously over everything. Serve immediately while the salmon is still warm and the vegetables are at their best.
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Crisp vegetables, roast meats, bake snacks, and reheat leftovers quickly for easy, flavorful home cooking.
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Flaky, perfectly cooked One-Pan Roast Salmon served over caramelized vegetables, garnished with fresh herbs and lemon slices on a rustic plate. Pin
Flaky, perfectly cooked One-Pan Roast Salmon served over caramelized vegetables, garnished with fresh herbs and lemon slices on a rustic plate. | toastybasil.com

There was a Tuesday evening when my daughter watched me make this and asked if she could help with the dressing, and suddenly we were tasting different variations together—a little more lemon here, extra capers there—and she decided it needed more parsley than the recipe called for, and you know what, she was right. Food tastes better when you've had a hand in it, even if that hand belongs to someone half your size asking a million questions.

Timing and Flexibility

The beauty of this recipe is that it works with your schedule, not against it. You can slice your vegetables an hour ahead and store them in the fridge, and the dressing actually tastes better if you make it 30 minutes early so the flavors settle. If you're running behind, you can even swap the salmon for trout or cod—anything that cooks through in roughly the same time will work beautifully on that sheet pan.

Making It Your Own

I've learned that recipes are more like suggestions than laws, especially when you understand what's happening in the pan. The dressing is incredibly flexible—if you don't have capers on hand, a finely minced anchovy adds the same salty punch, or skip them entirely and add more lemon zest. The vegetables can change with the season too; asparagus works wonderfully in spring, and Brussels sprouts add a nutty depth in fall.

Serving Suggestions and Pairings

This dish stands perfectly on its own, but I've found that a side of roasted potatoes makes it feel heartier, or steamed rice if you want something lighter. A crisp white wine like sauvignon blanc or a light rosé complements the salmon and parsley without competing for attention. The best part is that leftovers are delicious at room temperature the next day, which means lunch is already handled.

  • Serve with a simple green salad dressed in lemon vinaigrette to keep things bright and fresh.
  • If you're feeding people with dietary restrictions, double-check that your capers and mustard are certified gluten-free, though most are.
  • Make the dressing up to two hours ahead and store it in a jar at room temperature so the flavors meld together.
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Close-up of a juicy One-Pan Roast Salmon fillet drizzled with zesty parsley dressing, surrounded by roasted leeks and onions on a baking sheet. Pin
Close-up of a juicy One-Pan Roast Salmon fillet drizzled with zesty parsley dressing, surrounded by roasted leeks and onions on a baking sheet. | toastybasil.com

This recipe has become my go-to when I want to feel competent in the kitchen without spending hours there, and honestly, that's what good cooking is really about. It's simple enough that you can make it on a tired Wednesday, but flavorful enough that you'll genuinely enjoy every bite.

Recipe Q&A

Can I use frozen salmon fillets?

Yes, but make sure to thaw them completely in the refrigerator overnight before cooking. Pat them dry with paper towels to ensure proper roasting and seasoning.

What can I substitute for leeks?

You can use sliced fennel bulb, additional red onion, or even thick slices of white onion. Adjust the roasting time slightly depending on the vegetable's density.

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. It should be opaque throughout with a slightly pink center for optimal moisture.

Can I make the parsley dressing ahead of time?

Absolutely. Prepare the dressing up to 2 days in advance and store it in an airtight container in the refrigerator. Stir well before serving as the oil may separate.

What sides pair well with this dish?

Roasted potatoes, steamed rice, quinoa, or crusty bread work beautifully. A simple green salad or roasted asparagus also complement the flavors nicely.

Can I use a different type of fish?

Yes, trout, cod, halibut, or arctic char are excellent substitutes. Adjust cooking time based on the thickness of the fillets to prevent overcooking.

Roast Salmon With Leeks Onions

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

Prep duration
15 min
Cooking duration
25 min
Complete duration
40 min


Skill level Easy

Origin Modern European

Yield 4 Portions

Dietary specifications Dairy-free, Gluten-free, Low-Carb

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

Directions

Step 01

Preheat Oven: Preheat the oven to 400°F.

Step 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.

Step 03

Initial Roast: Roast the vegetables for 10 minutes.

Step 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.

Step 05

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

Step 06

Make Parsley Dressing: In a small bowl, combine parsley, garlic, Dijon mustard, capers, lemon zest, olive oil, and lemon juice. Stir well. Season with salt and pepper to taste.

Step 07

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

Necessary tools

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

Allergy information

Review each component for possible allergens and if uncertain, we recommend consulting with a healthcare professional.
  • Contains fish (salmon)
  • Contains mustard

Nutrient breakdown (per portion)

These values are provided as a general guide and shouldn't replace professional medical advice.
  • Calories: 365
  • Fat: 23 g
  • Carbs: 10 g
  • Protein: 30 g