1 Preheat oven to 350°F. Lightly grease and flour 9x5-inch loaf pan. Mix flour, baking powder, baking soda, salt and cinnamon in medium bowl. Set aside.
2 Beat butter and sugar in large bowl with electric mixer on medium speed until light and fluffy. Add eggs and banana flavor; mix well. Add bananas and sour cream; beat on low speed until well blended. Gradually beat in flour mixture until well mixed. Stir in walnuts. Pour into prepared pan.
3 Bake 55 to 60 minutes or until toothpick inserted in center comes out clean. Cool in pan 10 minutes. Remove from pan; cool completely on wire rack.