Preheat oven to 325 degrees F. Grease and flour 10" tube pan.
Combine cake mid and pudding mix.
In separate bowl, beat eggs, oil, vanilla, rum and pineapple. Slowly add cake mixture. Spread macadamia nuts evenly over the bottom of prepared pan and cover with batter.
Bake at 350 degrees F for 60 minutes or until toothpick comes out clean when inserted into cake. Place on cooling rack.
Meanwhile make glaze by combining butter, water, and sugar in a sauce pan. Bring to a boil, then reduce heat to medium and boil rapidly. Stir constantly until reduced to a thick consistency. About 5 minutes. Remove from heat and add rum.
While cake is still warm poke holes all over top of cake with chopstick or toothpick. Spoon glaze over top of cake and allow to sit at room temp overnight. Refrigerate.