01 -
Preheat the oven to 190°C. Grease a 25 x 38 cm jelly roll pan thoroughly.
02 -
In a bowl, stir the mashed bananas with lemon juice and set aside.
03 -
In a second bowl, whisk together flour, baking soda, and salt until well blended.
04 -
Using an electric mixer, cream the softened butter and granulated sugar on medium speed until pale and fluffy.
05 -
Blend in the eggs one at a time, followed by the vanilla extract, mixing until fully incorporated.
06 -
Alternately add the banana mixture and the flour mixture to the creamed ingredients, mixing gently after each addition. Add the sour cream with the final portion of flour and mix just until combined. Do not overmix.
07 -
Transfer the batter into the prepared pan and spread it evenly using a spatula.
08 -
Bake for 20 to 25 minutes, or until a toothpick inserted into the centre comes out clean. Remove from oven and allow to cool completely on a wire rack.
09 -
For the frosting, melt butter in a saucepan over medium heat. Cook, stirring frequently, until the butter turns golden brown and develops a nutty aroma, about 3 to 5 minutes. Immediately remove from heat and transfer to a clean bowl to cool slightly.
10 -
Beat in the powdered sugar, vanilla extract, and milk gradually until the frosting is smooth and creamy.
11 -
Spread the brown butter frosting evenly over the cooled bars. Cut into squares and serve.