I've always loved salmon cooked to medium-rare in a low temperature oven, but with only one oven, that rules out vegetables roasted to go along side of the salmon. In an attempt to have it all, I started the vegetables in a hot oven first, dropped the temperature and added the salmon. I was thrilled to find the meal was easy (everything cooked in one pan) and starting the salmon in a cooling oven produced the best salmon I ever tasted - rich, moist...luxurious. —Leila
Preheat oven to 425°F . Preheat a half sheet pan (12"x17") for about 10 minutes.
Clean and halve fennel. Cut out tough core and slice fennel into 1/4" slices.
Remove hot pan from oven and place one tablespoon of butter in pan, swirling to coat bottom. Place sliced fennel, green beans, and whole grape tomatoes in the pan. Drizzle with 2 tablespoons olive oil and toss so that the vegetables are evenly coated. Sprinkle with about 3/4 teaspoon kosher salt and 1/4 teaspoon ground black pepper. Place in hot 425°F oven for 20 minutes.
After 20 minutes, reduce the oven temperature to 250°F . Remove sheet pan from oven, and using a spatula, stir roasting vegetables. Return pan to oven and set timer for an another 20 minutes. Remove the salmon from the refrigerator, remove any pin bones you may find. Cut salmon into 4 or 5 pieces, each piece approximately 2" wide, leaving the skin on. Salt and pepper the salmon and leave at room temperature for the 20 minutes to come to room temperature.
After 20 minutes, remove pan from the oven and push the vegetables to the side of the pan to make room in the center for the salmon and lemon. Cut the lemon in half along the equator. Place lemon, cut side down in the pan along with the salmon pieces (skin side down) and 2 tablespoons drained capers. Return pan to the oven for 25-30 more minutes until the salmon is medium-rare (115°F).
To serve, using a spatula, carefully lift separating salmon from the skin and discard skin (baking with the skin on helps retain moisture), squeeze warm lemon halves over the fish, top fish with warm capers and enjoy.