Black-Bottom Banana Bars

1/2 c. butter, softened
1 c. sugar
1 egg
1 tsp. vanilla extract
1 1/2 c. mashed ripe bananas (about 3 medium)
1 1/2 c. all-purpose flour
1 tsp. baking powder
1 tsp. baking soda
1/2 tsp. salt
1/4 c. baking cocoa

In large bowl cream butter and sugar. Add egg and vanilla; beat until thoroughly combined. Blend in bananas. Combine flour, baking powder, baking soda and salt; add to creamed mixture and mix well. Divide batter in half. Add cocoa to half; spread into greased 13-inch by 9-inch baking pan. Spoon remaining batter on top and swirl with a knife. Bake at 350° for 25 minutes or until toothpick inserted near center comes out clean. Cool in pan on wire rack. Cut into bars. Makes 2 1/2 – 3 dozen.