Preheat the oven to 350 degrees F (175 degrees C). Grease a 12-cup muffin tin with butter or line with parchment paper liners.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, mash the bananas with a fork. Stir in the melted butter, sugar, eggs, cacao powder, and vanilla extract, and mix until smooth.
Add the dry ingredients to the wet ingredients and mix until just combined. Do not overmix.
Divide the batter evenly among the prepared muffin cups. Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the muffins to cool in the pan for 5 minutes before transferring to a wire rack to cool completely.
Interesting Facts
Bananas are a great source of potassium, fiber, and vitamin C.
Cacao powder is a good source of antioxidants and minerals.