Preheat over to 350; grease and flour a 10" bundt pan. CAKE: Put chopped pecans in bottome of bundt pan. Cream butter and sugar. Add eggs one at a time, mixing well after each one. Sift the lower, baking powder, baking soda and salt together and add alternatively with the buttermilk to the egg mixture. Stir in vanilla and rum extracts. Pour batter into prepared pan over nuts. Bake at 350 for 1 hour. Cool cake in pan and turn out on a serving platter. Pierce cake from top to bottom with a skewer. FILLING: Cut cake in half crosswise, spread filling on bottom layer and replace top layer. Pierce more holes, being careful not toput too much pressure on the cake. GLAZE: Melt butter, stir in water and sugar. Boil for 5 minutes, stirring continuously. Remove from heat and stir in rum. Slowly drizzle glaze over top of cake a little at a time. Allow cake to absorb glaze before adding more.