Preheat oven to 325 degrees F.
Grease and flour a 10-inch bundt pan. Sprinkle pecans over the bottom.
In a large bowl, with a mixer, combine yellow cake mix, vanilla instant pudding mix, eggs, water, oil and Irish Cream liqueur.
Pour the batter over nuts in pan. Bake for 60 minutes or until toothpick inserted in center of cake comes out clean.
Cool for 10 minutes in the pan. Flip the cake out of the pan and cool completely on a wire rack.
While the cake is cooling, make the glaze. Combine butter, water and sugar in a small saucepan. Bring to a boil and continue boiling for 5 minutes, stirring constantly. Remove from heat and add Irish Cream liqueur.
Prick top and sides of cooled cake with a skewer. Spoon glaze over top and brush onto sides of the cake. Allow the cake to absorb the glaze and repeat until most of the glaze is used. Save some glaze to pour over sliced pieces. (You'll be glad you did.)