Preheat oven 350°F. In large bowl, cream butter and sugar with electric mixer until light and fluffy. In medium bowl, combine flour, baking soda, and salt; set aside. Add eggs, vanilla and banana; mix well. Add flour mixture alternately with sour cream; blend thoroughly but do not overmix. Pour into prepared pans. Bake 20-25 minutes or until toothpick inserted comes out clean. Cool 10 minutes in pan on rack; remove and cool completely before decorating.