Heat oven to 350 degrees F. Grease and flour a 10-inch tube pan.
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 butter mixture, mixing
until blended. Pour into prepared tube pan; set aside.
Combine 1/2 cup flour and remaining ingredients; sprinkle over batter.
55 minutes or until a wooden pick inserted in 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.