Rinse fish thoroughly in cold water; pat dry, and set aside.
Combine cracker crumbs, bread cubes, celery, onion, parsley, melted butter, egg, 1/2 teaspoon salt, and 1/2 teaspoon pepper in a medium mixing bowl; mix well. Set aside.
Sprinkle fish inside and out with remaining salt and pepper. Rub with 1 tablespoon butter; dredge in flour. Stuff cavity with cracker crumb mixture.
Place fish in an aluminum foil-lined 13- x 9- x 2-inch baking pan. Lay bacon slices over fish. Pour tomatoes over fish. Bake, uncovered, at 350° for 1 hour and 15 minutes or until fish flakes easily when tested with a fork.
Transfer fish to a warm serving platter, and serve with lemon slices.