Beat 1/2 cup butter at medium speed with an electric mixer until creamy; gradually add sugar, beating well.
Add eggs, one at a time, beating after each addition.
Stir in mashed bananas, rum and vanilla extract.
Combine 1 1/2 cups flour and next 4 ingredients; add to the butter mixture, mixing until blended. Pour into prepared tube pan; set aside.
Combine 1/2 cup flour and remaining ingredients;; sprinkle over batter, Bake for 55 minutes, or until a wooden toothpick inserted into center of cake comes out clean. Cool in pan on a wire rack for 10 to 15 minutes; remove from pan and let cool completely on wire rack.