Pour the batter in to the bundt and place in a 325 oven for 50 minutes to an hour, or until a toothpick comes out clean.
While the cake is baking, in a saucepan, combine butter, white sugar, the white rum and the water and bring to a boil and cook for 3 –5 minutes.
When you take the rum cake out of the oven, flip it over on a rack on a cookie sheet, and immediately pour the glaze over the cake while it's still warm.