1Preheat oven to 350 degrees F (175 degrees C). Grease a 10x15 inch jellyroll pan.
2In a large bowl, cream together the butter and sugar until smooth. Beat in the eggs, one at a time, then stir in the sour cream and vanilla. Combine the flour, baking soda and salt; stir into the batter. Finally, mix in the mashed banana. Spread evenly into the prepared pan.
3Bake for 20 to 25 minutes in the preheated oven, until a toothpick inserted into the center comes out clean. Allow bars to cool completely before frosting with the cream cheese frosting.
Footnotes
Tip
Aluminum foil can be used to keep food moist, cook it evenly, and make clean-up easier.