- 1 5–6 pound head-and tail-on salmon or arctic char, cleaned
- 10 cups kosher salt (from about one 48-ounce box), plus more
- 1 grapefruit, thinly sliced
- 2 lemons, thinly sliced
- 1/2 bunch dill
- 1/2 bunch tarragon
- 1 small shallot, finely chopped
- 1/2 cup dry white wine
- 3/4 cup (1 1/2 sticks) chilled unsalted butter, cut into pieces
- 2 tablespoons crème fraîche
- 1 teaspoon finely grated grapefruit zest
- 1 teaspoon fresh grapefruit juice
- 1 teaspoon finely grated lemon zest
- 3 teaspoons fresh lemon juice, divided
- Kosher salt
- 1 cup fresh parsley leaves with tender stems
- 1/3 cup fresh dill leaves
- 1/3 cup fresh tarragon leaves
- 2 tablespoons chopped capers
- 2 teaspoons caraway seeds
- Salmon will be closer to 5 pounds; arctic char closer to 6 pounds. Not all shops will have whole fish this large on hand; call ahead so they can order it.
- Place a rack in the center of oven and preheat to 400°. Season inside of salmon with salt. Stuff with one-third of grapefruit slices, lemon slices, dill sprigs, and tarragon sprigs.
- Mix 10 cups salt and 1 1/2 cups water in a large bowl, adding more water as needed, until mixture is the texture of wet sand. Spread a thin layer of salt mixture on a rimmed baking sheet roughly the same shape and size as fish.
- Top salt mixture with another third of grapefruit and lemon slices and dill and tarragon sprigs; set salmon on salt bed and top with remaining citrus and herbs. Pack remaining salt mixture over fish, leaving head and tail peeking out.
- Roast salmon until just cooked through (poke a paring knife or metal skewer though the salt and into the flesh; it should feel warm to the touch when removed), 40–50 minutes.
- While salmon is cooking, simmer shallot and wine in a small saucepan until only 2 tablespoons liquid remains, 8–10 minutes. Whisking constantly, add butter a piece at a time, incorporating completely before adding the next piece, to make a glossy, emulsified sauce.
- Whisk crème fraîche, grapefruit zest, grapefruit juice, lemon zest, and 1 teaspoon lemon juice into sauce; season with salt. Reduce heat to low and keep sauce warm while you finish the dish.
- Remove salmon from oven and using a knife or the edge of a fish spatula, crack salt crust and remove (it should come off in large pieces); let salmon sit 5 minutes before serving.
- Meanwhile, toss parsley, dill, tarragon, capers, caraway seeds, and remaining 2 teaspoons lemon juice in a medium bowl; season herb salad with salt. Serve salmon with beurre blanc and herb salad.