Banana Bread

I had a really great recipe for banana bread that had sour cream in it, and it has been lost to the ages.  This one looks pretty similar, from what I can remember.

4 very ripe bananas, divided 2 cups all-purpose flour 1 cup white sugar 1 1/2 teaspoons baking powder 1/2 teaspoon salt 1/2 teaspoon ground cinnamon 2 teaspoons white sugar 1/2 cup chopped walnuts (optional) 3/4 cup butter, melted and cooled 2 large eggs 1/3 cup sour cream 1 teaspoon vanilla extract   Preheat the oven to 350.  Grease a 5x9 loaf pan. Mash 2 bananas in a bowl with a fork. Place remaining 2 bananas in a separate bowl with 1 cup sugar and beat the bananas and sugar with an electric mixer until creamed and fluffy, 3 minutes. Beat in melted butter, eggs, sour cream, and vanilla extract until thoroughly combined.   Whisk flour, baking powder, and salt together in a bowl and stir the flour mixture into banana-sugar mixture. Fold in mashed bananas and walnuts. Pour batter into prepared loaf pan and tap the pan on the counter several times to remove any air pockets. Stir 2 teaspoons sugar with cinnamon in a small bowl and sprinkle the cinnamon sugar over the top of the loaf.   Bake in the preheated oven until bread is golden brown on top and set in the center, 1 hour and 15 minutes; rotate bread pan in oven halfway through baking. Cool in the pan for 10 minutes before removing to finish cooling on a wire rack.