1. If using frozen fish, unwrap and let the fish stand at room temperature for 20 minutes.
2. Preheat the oven to very hot (450°). Grease an 8 x 8 x 2-inch square baking dish.
3. Cut or separate the fish into 4 equal portions. (Be careful cutting frozen fish, since the center will still be hard and frozen.) Combine the bread crumbs and the salt on a piece of wax paper. Dip the fish into the milk, then roll in the crumb mixture to evenly coat. Place the fish in the prepared baking dish. Drizzle the fish with the melted butter.
4. Bake the fish in the preheated very hot oven (450°) for about 30 minutes for frozen fish, or about 10 minutes for fresh fish, or until the fish flakes easily when pierced with a fork. Serve the fish immediately. (Both fresh and frozen fish may contain bones, so be sure to remove before serving or as you eat.)