to the cake batter, then brush a mixture if 1 tablespoon of rum mixed with 1 tablespoon water on the still warm cake, and put a 1 tablespoon in the frosting. It depends on how much you want to spike the flavor of the cake! My preference it to add 2 tablespoons of dark rum to the batter and then brush the top with 1 tablespoon of dark rum mixed with 1 tablespoon of water. For me, that’s just the right amount of rum. I bake this cake in a 9X13 inch Pyrex baking dish and it’s perfectly done in 30 minutes in my oven.