• Preheat oven to 400°.
• Place banana slices, brown sugar, and 1 tablespoon butter in an 8-inch square baking dish.
• Bake for 35 minutes, stirring after 17 minutes. Cool slightly. Reduce the oven temperature to 375°.
• Lightly spoon cake flour into dry measuring cups; level with a knife. Combine flour, baking soda, and baking powder in a medium bowl. Set aside.
• In another medium bowl, combine banana mixture, buttermilk, and vanilla. Set aside.
• In a large mixing bowl, using an electric mixer on medium speed, mix together the butter and granulated sugar until well blended.
• Add eggs to sugar mixture and mix well. Add flour mixture to sugar mixture to alternating with banana mixture, beginning and ending with flour mixture.
• Pour batter into a 13 x 9–inch baking pan coated with baking spray. Bake for 20 minutes or until a wooden pick inserted in center comes out clean.
• Cool completely in pan on a wire rack. .

To prepare frosting

• Melt butter in a small saucepan over medium heat; cook 4 minutes or until lightly browned. Cool slightly.
• Combine browned butter, powdered sugar, cream cheese, and 1 teaspoon vanilla in a medium bowl; beat with a mixer until smooth.
• Spread frosting over cooled bars. Sprinkle with pecans.