Preheat the Oven: Set your oven to 350°F (175°C).

Prepare the Pan: Line a 9×13-inch baking pan with parchment paper for easy removal.

Mash Bananas: In a large bowl, mash the ripe bananas with a fork until mostly smooth.

Mix Wet Ingredients: Stir in the melted butter until combined. Add brown sugar, eggs, and vanilla extract, whisk until smooth.

Combine Dry Ingredients: In a separate bowl, whisk together flour, baking powder, salt, cinnamon, and nutmeg.

Fold Dry into Wet: Gently fold dry ingredients into the wet mixture until just combined—be careful not to overmix.

Pour and Bake: Pour the batter into the prepared pan and bake for 25 to 28 minutes. Check for doneness with a toothpick; it should come out with a few moist crumbs.

Cool Completely: Allow the brownies to cool completely in the pan before frosting.

Brown the Butter: In a saucepan, melt the butter until golden brown, then let it cool.

Mix Frosting Ingredients: In a bowl, beat softened cream cheese with cooled butter, then add powdered sugar and vanilla. Beat until fluffy.

Frost the Brownies: Spread the frosting over the cooled brownies, slice into 16 bars, and serve.