Roast Salmon With Leeks Onions

Featured in: Simple Spiced Skillet Meals

This one-pan wonder delivers perfectly roasted salmon nestled among caramelized leeks and red onions, all brightened with a punchy parsley dressing. The salmon cooks beautifully skin-side down while the vegetables turn tender and sweet. The fresh herb dressing—packed with parsley, capers, garlic, and lemon—adds vibrant flavor. Ready in just 40 minutes with minimal dishes, this gluten-free and dairy-free dish is ideal for busy weeknights or elegant enough for entertaining.

Updated on Fri, 30 Jan 2026 15:36:00 GMT
Golden-brown roasted leeks and onions cradle tender, flaky salmon fillets, garnished with bright green parsley dressing. Pin it
Golden-brown roasted leeks and onions cradle tender, flaky salmon fillets, garnished with bright green parsley dressing. | spiceshallows.com

The scent of roasted leeks hits differently on a rainy Wednesday. I was standing at the counter, debating whether to order takeout again, when I remembered I had salmon in the fridge and a bundle of leeks going soft. What started as a lazy necessity turned into something I now make on purpose. The whole thing comes together on one pan, which means less scrubbing and more time to sit down and actually enjoy dinner.

I made this for a friend who swore she hated cooked onions. She ate two servings and asked for the recipe before she left. Watching her scrape up every bit of that parsley dressing with a fork was all the validation I needed. Sometimes the simplest meals are the ones people remember, not because theyre complicated, but because they just work.

Ingredients

  • Salmon fillets: Skin-on keeps the fish moist and gives you crispy edges if you let it sit undisturbed.
  • Leeks: They go sweet and tender in the oven, way more interesting than plain onions alone.
  • Red onion: Adds a slight sharpness and gorgeous color that looks great on the plate.
  • Olive oil: For roasting the vegetables, use regular olive oil, save the fancy stuff for the dressing.
  • Sea salt and black pepper: Season everything well, especially the vegetables, they need it.
  • Lemon slices: They roast right on top of the salmon and add a subtle citrus perfume.
  • Fresh flat-leaf parsley: The backbone of the dressing, do not skip or substitute with dried.
  • Garlic clove: One small clove is enough, it mellows into the dressing without overpowering.
  • Dijon mustard: Adds body and a gentle tang that ties the dressing together.
  • Capers: Salty, briny little bursts that make the dressing come alive.
  • Lemon zest and juice: Brightens everything, use a microplane for the zest to avoid bitterness.
  • Extra-virgin olive oil: This is where the good oil matters, it coats your tongue and carries all the flavors.

Instructions

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Get the oven hot:
Preheat to 400°F so the vegetables start caramelizing right away. A cold oven will steam them instead of roasting.
Prep the vegetables:
Toss leeks and red onion with olive oil, salt, and pepper on a large baking sheet. Spread them out so they roast evenly, not steam in a pile.
Start roasting the veg:
Let them go for 10 minutes to get a head start. Theyre denser than the salmon and need the extra time.
Add the salmon:
Nestle the fillets skin-side down right among the vegetables and top with lemon slices. The fish will finish cooking at the same time the veg get tender.
Finish roasting:
Roast for 12 to 15 minutes until the salmon flakes easily. Dont overcook it or it gets dry and chalky.
Make the dressing:
While everything roasts, chop parsley finely and mix with garlic, mustard, capers, zest, oil, and lemon juice. Taste it and adjust salt and pepper, it should be punchy.
Plate and serve:
Transfer salmon and vegetables to plates and spoon the dressing generously over the top. Serve immediately while everything is warm.
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Keep kitchen knives sharp for safer slicing, chopping, and precise prep during everyday cooking.
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Freshly prepared One-Pan Roast Salmon with leeks and onions on a white ceramic platter, ready to serve. Pin it
Freshly prepared One-Pan Roast Salmon with leeks and onions on a white ceramic platter, ready to serve. | spiceshallows.com

I served this on a night when I was too tired to care about impressing anyone. My partner looked up halfway through and said it tasted like something from a restaurant. That kind of accidental win is what keeps me coming back to simple recipes like this one.

Serving Suggestions

This dish is complete on its own, but I like pairing it with roasted baby potatoes or a scoop of steamed rice to soak up the dressing. A simple green salad with lemon vinaigrette keeps the meal light but satisfying. If youre feeding a crowd, double the dressing recipe because people will want extra.

Storage and Reheating

Leftovers keep well in the fridge for up to two days in an airtight container. Reheat gently in a low oven or eat it cold over greens for lunch. The dressing loses some brightness after a day, so if you plan to meal prep, store it separately and drizzle fresh before serving.

Swaps and Variations

If you cant find leeks, use thinly sliced fennel or shallots instead. Trout and cod both work beautifully in place of salmon, just adjust the cooking time slightly depending on thickness. For a spicier kick, add a pinch of crushed red pepper flakes to the dressing.

  • Try swapping parsley for cilantro and adding lime juice for a different vibe.
  • Add cherry tomatoes to the pan halfway through roasting for extra sweetness.
  • Top with toasted pine nuts or slivered almonds for crunch.
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Citrusy parsley dressing drizzled over perfectly cooked One-Pan Roast Salmon, highlighting the caramelized red onion wedges. Pin it
Citrusy parsley dressing drizzled over perfectly cooked One-Pan Roast Salmon, highlighting the caramelized red onion wedges. | spiceshallows.com

This is the kind of recipe that makes weeknight cooking feel less like a chore and more like something you actually look forward to. Keep it in your rotation and youll always have an answer when someone asks whats for dinner.

Recipe Q&A

Can I use frozen salmon fillets?

Yes, but ensure they're completely thawed and patted dry before roasting. Excess moisture can prevent proper browning and may increase cooking time slightly.

What other vegetables work well with this preparation?

Fennel, cherry tomatoes, asparagus, or zucchini are excellent alternatives. Just adjust roasting times based on the vegetable's density—softer vegetables need less pre-roasting time.

How do I know when the salmon is perfectly cooked?

The salmon should flake easily with a fork and reach an internal temperature of 145°F. It should appear opaque throughout with a slightly translucent center for moist, tender results.

Can I make the parsley dressing ahead of time?

Absolutely. Prepare the dressing up to 24 hours in advance and store it refrigerated in an airtight container. Bring to room temperature and stir well before serving for best flavor.

What's the best way to store leftovers?

Store salmon and vegetables separately from the dressing in airtight containers for up to 3 days. Reheat gently in a 300°F oven for 8-10 minutes, then add fresh dressing before serving.

Can I substitute the parsley dressing with something else?

Try a lemon-butter sauce, tahini drizzle, or chimichurri for variety. Each brings different flavor profiles while complementing the roasted salmon and vegetables beautifully.

Roast Salmon With Leeks Onions

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

Prep time
15 minutes
Cook time
25 minutes
Overall time
40 minutes
Created by James Fisher


Skill level Easy

Cuisine Style Modern European

Makes 4 Portions

Diet details Without Dairy, No Gluten, Reduced Carbs

What You Need

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 tbsp olive oil
05 1/2 tsp sea salt
06 1/4 tsp 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 tsp Dijon mustard
04 1 tsp capers, drained and chopped
05 1/2 tsp lemon zest
06 3 tbsp extra-virgin olive oil
07 1 tbsp fresh lemon juice
08 Salt and pepper, to taste

Directions

Step 01

Preheat Oven: Heat oven to 400°F.

Step 02

Prepare Vegetables: Arrange 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.

Step 03

Initial Vegetable Roast: Roast vegetables for 10 minutes until they begin to soften.

Step 04

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

Step 05

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

Step 06

Prepare 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

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

Tools & Equipment

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

Allergy alerts

Review every ingredient for allergens and consult your physician or specialist if you’re unsure.
  • Contains fish (salmon)
  • Contains mustard

Nutritional info (for each serving)

This info is for reference only and isn’t medical advice.
  • Caloric Value: 365
  • Fats: 23 g
  • Carbohydrates: 10 g
  • Proteins: 30 g