Step 1

Preheat an oven to 425°F (220°C). Lightly oil a rimmed baking sheet with olive oil.

Step 2

Cut off the stems and fronds from the fennel bulbs. Finely chop the fronds from 1 bulb and reserve the fronds from another for garnish. Discard the remaining fronds and any stems. Cut each fennel bulb in half lengthwise and trim away the tough core. Cut the bulbs crosswise into thin slices.

Step 3

Scatter about half the leeks and half the sliced fennel bulbs evenly over the bottom of the prepared baking sheet. Lightly season with salt and pepper. Rinse the fillets under cold running water and pat dry with paper towels. Arrange the fillets, skin side down, on top of the vegetables. Season with salt, pepper, half of the thyme and about 1/3 cup (1/3 oz./10 g) of the chopped fennel fronds. Drizzle the fillets with half of the lemon juice and 1 1/2 Tbs. olive oil.

Step 4

Roast the salmon until opaque throughout when pierced with a knife, about 20 minutes, depending on the thickness of the fish; allow about 10 minutes for each inch (2.5 cm).

Step 5

Meanwhile, toss the remaining chopped leeks and fennel bulbs in a baking dish with the remaining thyme, chopped fennel fronds, lemon juice and 1 1/2 Tbs. olive oil. Sprinkle with salt and pepper and transfer to the oven. Roast the vegetables alongside the fish until the vegetables are lightly browned and tender, about 15 minutes.

Step 6

Using a spatula, transfer the leeks to a warmed platter and top with the salmon. Garnish with the reserved fennel fronds and serve immediately. Serves 6.

Step 7

Adapted from Williams-Sonoma Year-Round Roasting (Weldon Owen, 2014)