Preheat your oven to 350°F (175°C). Grease and line a 9x13-inch pan.

In a medium bowl, whisk together the flour, baking powder, baking soda, cinnamon, and salt.

In a separate large bowl, beat the butter, granulated sugar, and brown sugar until light and fluffy. Add the eggs one at a time, mixing well after each.

Stir in the mashed bananas and vanilla extract.

Add half of the dry ingredients, mix gently, then add the buttermilk. Finish with the remaining dry ingredients. Don’t overmix—just until combined.

Pour the batter into the prepared pan and spread it evenly. Bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean.

Let the cake cool completely before frosting.

In a small saucepan, melt the butter over medium heat. Keep stirring until the butter turns golden brown and smells nutty—this should take about 5–7 minutes. Pour it into a bowl and let it cool to room temperature (don’t skip this).

Once cooled, beat the brown butter with cream cheese until smooth.

Add the vanilla extract and gradually mix in the confectioners’ sugar until the frosting is creamy and spreadable.

Frost the cooled cake and slice into squares.