An easy recipe for rum sauce is to melt 2 tablespoons rum, 2 tablespoons brown sugar and 1 tablespoon butter together in a glass dish until runny. For more sophisticated rum sauce, Betty Crocker and Pillsbury both have recipes.
To make Betty Crocker's rum sauce, mix 1/2 cup packed brown sugar, 1/2 cup butter or margarine, 2/3 cup whipping cream and 1/4 cup rum in a 1 1/2-quart saucepan. Heat to a boil over medium heat, and stir constantly. Boil the mixture for three to four minutes, while continuing to stir constantly until the mixture is slightly thickened. Serve the rum sauce warm, and store in a refrigerator covered. The rum may be substituted with 2 teaspoons of rum extract. This recipe is good to put on fresh fruit, ice cream or pound cake.
Pillsbury's rum sauce is made by mixing 1 cup brown sugar, 1/2 cup butter, 1/8 teaspoon salt, and 1 14-ounce can of sweetened condensed milk in a medium saucepan. Bring the mixture to a boil over medium heat, and stir constantly to prevent scorching. Cook until the sugar is dissolved, and remove from the heat. Stir in 1/4 cup dark rum and 2 teaspoons of vanilla. Reheat the sauce before serving, and store in the refrigerator. This recipe is suggested for ice cream.