3/4 cup regular flour
Combine 3/4 cup flour and 1/2 cup sugar in a bowl. Cut in butter with pastry blender or 2 knives until mixture is crumbly.
Reserve 1/2 cup of crumbs.
Add 1/4 cup sugar, eggs and vanilla to remaining crumb mixture. Beat until smooth.
Sift together 1 cup flour, baking powder, baking soda, salt, and cinnamon. Add dry ingredients alternately with combined bananas and buttermilk, beating well after each addition. Spread batter in a greased 10" pie plate. Sprinkle with reserved 1/2 cup crumbs.
Bake in a 375 degree oven 35 minutes or until cake tests done. Cool in pan on rack.