To make this dish, a horseradish-and-breadcrumb crust is patted on top of each fillet; the fillets are then broiled until golden brown.
Heat oven to 450 degrees; position rack 8 to 12 inches from heat. Place bread in the bowl of a food processor; pulse until coarsely chopped (1/4- to 1/8-inch pieces). Add 1 teaspoon salt, 1/4 teaspoon pepper, shallot, dill, horseradish, and 2 tablespoons olive oil. Pulse just until combined; set aside.
Rub bottom and sides of a 12-by-17-inch pan with olive oil. Place salmon on pan, spacing fillets 2 inches apart. Sprinkle salmon with remaining 1/2 teaspoon salt and 1/4 teaspoon pepper. Pat mixture onto top of each fillet. Bake until just cooked through, 5 to 6 minutes. Turn heat to broil, and cook until tops are a rich golden brown, 1 to 2 minutes. Serve immediately.