1. Place a rack in lower-middle of oven and heat to 400 degrees. Rub salmon and skin all over with 2 teaspoons oil, then season flesh with salt and pepper and set aside.
2. Thinly slice half of lemon; remove seeds, then transfer slices to a 13x9" baking dish. Squeeze 2 teaspoons juice from remaining lemon half; set juice aside. Add leeks and two-thirds of fennel to lemon slices, season with salt and pepper, and drizzle with 3 tablespoons oil. Toss until evenly coated, then spread into an even layer.
3. Roast until vegetables are sizzling and beginning to brown, 15 to 20 minutes. Remove baking dish from oven and lower temperature to 275 degrees. Stir vegetables, then push toward edges of dish and nestle salmon in center, skin side down. Return to oven and roast until salmon is just opaque and beginning to flake, 20 to 25 minutes.
4. Meanwhile, use a vegetable peeler or mandoline to shave asparagus into thin ribbons. Transfer to a medium bowl, then add radishes and remaining one-third of fennel. Toss to combine and set aside.
5. To serve, carefully transfer salmon to a platter. Add lemon juice and remaining 1 teaspoon oil to asparagus mixture; toss until coated, and season with salt and pepper to taste. Arrange mixture on top of salmon, letting some spill off onto platter, then sprinkle with reserved fennel fronds. Transfer leek mixture to a bowl and serve alongside salmon.
Source: Hannaford fresh Magazine, March - April 2020