Combine bananas and sour cream at medium speed in a blender until smooth. Set aside.
Combine ½ cup sugar, cinnamon, nuts, and melted butter, mixing well. Fold in remaining bananas. Set aside.
Cream softened butter and sugar until fluffy. Beat in eggs.
Sift together flour, baking powder, and soda. Add to creamed mixture alternately with sour cream mixture.
Spread half of the batter into greased 9-inch pan (*I found that I needed a larger pan than that.). Sprinkle with half of the sugar mixture. Repeat the process, using the remaining batter and sugar mixture.
Bake in a pre-heated 350-degree oven for 30 minutes or until done. (*Mine took about 50 minutes)