Preheat oven to 325 degrees. Grease and flour a 10" bundt pan. Sprinkle chopped nuts evenly over bottom of pan. In large bowl, combine cake and pudding mixes. Mix in eggs, 1/2 c water, oil, and 1/2 c rum. Blend well. Pour batter over chopped nuts in pan. Bake in preheated oven for 60 min or until a toothpick inserted into cake comes out clean. Let sit 10 min in pan, then turn out onto serving plate. Brush glaze over top and sides. Allow cake to absorb glaze and repeat until all glaze is used. To make glaze: In a saucepan, combine butter, 1/4 c water, and 1 c sugar. Bring to boil over med heat and continue to boil 5 min, stirring constantly. Remove from heat and stir in 1/2 c rum.