How to Make It
Combine first 4 ingredients (through garlic powder) in a medium bowl. Line a baking sheet with plastic wrap, leaving enough overhang to cover fish. Sprinkle 3 tablespoons salt mixture on plastic; place fish, skin side down, on salt mixture. Sprinkle remaining salt mixture on fish; press to adhere. Tightly wrap plastic around fish. Place a separate baking sheet on fish; weight with a cast-iron skillet. Chill 1 hour.
Unwrap and rinse fish; pat dry. Return to pan, and chill overnight.
Preheat grill to 180°F; maintain temperature 10 minutes. Push coals to one side; top with wood chips. (Or preheat one side of gas grill and wrap wood chips in foil.) Place fish on oiled grates over indirect heat. Grill, covered, until firm and golden, about 2 hours. Remove from grill; let stand 15 minutes.
Combine cream cheese and scallions; spread on bagel halves. Top with capers, tomatoes, fish, and dill.