Preheat the broiler and position a rack 6 inches from the heat.
In a small bowl, mash the garlic with the salt and pepper until a paste forms. Rub the snapper fillets with the paste.
In a saucepan, combine the soy, lemon juice, brown sugar and crushed red pepper. Bring to a boil over high heat, stirring until the sugar dissolves.
Brush a baking sheet with oil. Arrange the fillets on the baking sheet and pour half of the sauce over them. Broil for 8 minutes, or until the fillets are firm to the touch and opaque. Transfer the fish to a platter or plates. Drizzle with the remaining sauce and the melted butter.