Preheat your oven to 350°F (175°C).
In a mixing bowl, mash the ripe bananas until smooth.
Add the melted butter to the mashed bananas and mix well.
Stir in the sugar, vanilla extract, and mix until combined.
In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt.
Gradually add the dry ingredients to the banana mixture, stirring until just combined.
Pour the batter into a greased baking pan and spread it evenly.
Bake for 25 minutes or until a toothpick inserted into the center comes out clean.
Let the brownies cool in the pan before cutting into squares and serving.