In medium bowl, mix flour, baking powder and 1/2 teaspoon salt; set aside. In large bowl, beat 1/2 cup butter and 1 cup brown sugar with electric mixer on medium speed until light and fluffy. Add eggs, one at a time, beating just until combined. Beat in vanilla and bananas until well blended. Gradually add flour mixture, beating on low speed just until incorporated. Pour batter into pan.