Preheat oven to 350 degrees F (175 degrees C). Coat Bundt pan with 1 tablespoon melted butter. Sprinkle 1/4 cup of sugar and finely chopped pecans so that they coat the pan.
In a large bowl, combine the cake mix and instant pudding. Add 1/2 cup water, 1/2 cup oil, 1/2 cup rum and 4 eggs, mix until smooth and well blended. Spread evenly into the prepared pan.
Bake for 55 to 60 minutes in the preheated oven, or until a toothpick inserted into the cake comes out clean.
In a saucepan over medium heat, combine 1/4 cup butter, 1/2 cup sugar, 1/8 cup water and 1/8 cup rum. Bring to a boil, then remove from heat. Poke holes into the bottom of the cake using a fork. Pour glaze over the hot cake. Allow cake to cool completely before removing from pan.
