One-Pan Roast Salmon Leeks Onions

The leeks had been sitting in my crisper drawer for days, those tender green tops calling out every time I opened the fridge. I'd bought them on impulse after reading about how roasting transforms their sharp bite into something almost sweet. That Tuesday evening, with rain pattering against the kitchen window and zero motivation for a multi-pot cleanup, I decided to throw everything on one sheet pan with some salmon. The kitchen filled with this incredible aroma of roasting onions and citrus, and my roommate wandered in asking what restaurant I'd ordered from.

Last spring, my sister came over feeling completely burned out from work. I made this exact recipe, and we stood at the counter eating directly off the baking sheet because neither of us had the energy to plate properly. She took three bites and went quiet, then looked at me with this genuine smile and said this was exactly what she needed. Sometimes the simplest food hits hardest.

Ingredients

• Salmon fillets: Skin-on helps keep the fish moist during roasting, and the skin gets wonderfully crispy if you want to eat it
• Leeks: The white and light green parts sweeten dramatically in the oven, developing a flavor almost like mild roasted onions
• Red onion: Adds beautiful color and a caramelized sweetness that pairs perfectly with the bright parsley topping
• Olive oil: Use a decent quality one here since the dressing is so simple and the oil really shines through
• Fresh parsley: Flat-leaf has better flavor than curly, and lots of it is key to cutting through the rich salmon
• Dijon mustard: Just a tiny bit emulsifies the dressing and adds that subtle sharpness that makes everything pop

Instructions

Prep your oven and vegetables:

Crank that oven to 400°F and slice your leeks into half-inch rounds, then cut your onion into wedges. Spread them across a large baking sheet in a single layer so they roast instead of steam.

Give the vegetables a head start:

Drizzle the leeks and onions with olive oil, sprinkle with salt and pepper, then toss them with your hands until everything's coated. Pop them in the oven for about 10 minutes to start softening up.

Nestle in the salmon:

Pull the baking sheet out, move some vegetables aside, and place your salmon fillets skin-side down right among the leeks and onions. Tuck some lemon slices on top of each piece of fish.

Finish roasting everything together:

Return the pan to the oven for another 12 to 15 minutes, until the salmon is just opaque and flakes easily with a fork. The vegetables should be tender and starting to turn golden at the edges.

Whip up the parsley dressing:

While everything roasts, chop your parsley finely and combine it in a small bowl with minced garlic, Dijon mustard, chopped capers, lemon zest, olive oil, and lemon juice. Stir it really well and season to taste.

Plate and drizzle generously:

Transfer the salmon and roasted vegetables to plates, and spoon that bright green dressing all over everything. The contrast of warm, roasted fish with the cool, zesty topping is absolute magic.

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This recipe has become my go-to for dinner parties because it looks impressive but requires almost no active cooking time. I love watching people's faces when they take that first bite, the combination of warm roasted salmon and cool bright parsley catching them completely off guard.

Making It Your Own

I've played around with different fish over the months, and while salmon remains my favorite, trout works beautifully too. The oilier the fish, the better it pairs with that punchy parsley dressing. Cod is lighter and might need an extra drizzle of olive oil at the end.

Timing Is Everything

What I love about this recipe is how the vegetable head start means everything finishes at the same time. No half-cooked fish or mushy vegetables, just perfectly coordinated timing that feels almost professional. The key is that initial 10 minute roast without the fish.

Side Dish Magic

Most of the time I serve this straight from the baking sheet with maybe some crusty bread to sop up those roasting juices. But if you want something more substantial, buttery roasted potatoes or fluffy steamed rice never fail to complete the meal.

• Reserve a little extra parsley for garnish because the bright green against the roasted salmon looks stunning
• The dressing keeps in the fridge for a couple days and is incredible on grilled chicken the next night
• If you're serving this to guests, have everything prepped before they arrive so you can just pop it in the oven

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There's something deeply satisfying about a meal that comes together this easily but tastes like it took hours. Hope this becomes a weeknight staple in your kitchen too.

Recipe FAQs

→ Is this dish gluten-free?

Yes, this preparation is naturally gluten-free. Always double-check ingredient labels, especially for items like Dijon mustard, to ensure they meet your dietary needs.

→ Can I substitute the salmon?

Absolutely. If you prefer, trout or cod would make excellent alternatives. Adjust cooking time slightly based on the thickness of your chosen fish.

→ What are some good serving suggestions?

For a heartier meal, consider serving alongside roasted potatoes, fluffy couscous, or steamed rice. A simple green salad also complements the rich flavors beautifully.

→ How can I add more spice or flavor?

To introduce a bit of heat, sprinkle a pinch of crushed red pepper flakes into the parsley dressing. You could also add a dash of smoked paprika to the vegetables before roasting.

→ Can I prepare the dressing in advance?

Yes, the parsley dressing can be made up to 24 hours ahead of time. Store it in an airtight container in the refrigerator and give it a good stir before serving.

→ How do I know when the salmon is cooked through?

Salmon is typically done when it flakes easily with a fork and reaches an internal temperature of 145°F (63°C). The cooking time will vary slightly depending on the thickness of your fillets.