IN a large resealable plastic bag, combine the salmon and WHOLE30 Elderberry Vinaigrette. Seal bag and turn to coat salmon. Marinate in the refrigerator at least 30 minutes or up to 1 hour.
PREHEAT oven to 425°F. Remove salmon from the marinade; discard the marinade. Place salmon on one half of a large parchment-lined rimmed baking sheet. Season with ¼ teaspoon each of the coarse salt and black pepper.
PLACE asparagus on the other half of the prepared baking sheet. Drizzle with the olive oil and season with the remaining 1/2 teaspoon salt and 1/4 teaspoon black pepper. Toss to coat; arrange in a single layer. Place grapefruit slices on salmon and asparagus.
ROAST salmon until it flakes easily when tested with a fork (4 to 6 minutes per half-inch thickness), and asparagus and grapefruit are tender.* Cut around grapefruit rind and serve on top of salmon and asparagus.
*For a pretty presentation, after baking turn your oven to broil. Place the baking sheet under the heat and broil until the grapefruit is lightly charred, about 1 minute.