Preheat your oven to 350°F (175°C) and grease a 9-inch loaf pan with butter or baking spray.

In a large mixing bowl, combine the melted butter, brown sugar, and white sugar until smooth.

Stir in the sour cream, then add the eggs one at a time, whisking well after each addition.

Mash the ripe bananas in a separate bowl and fold them into the wet mixture.

Sprinkle the flour, baking soda, baking powder, salt, and cinnamon over the wet ingredients and gently mix.

Pour the batter into the prepared pan and bake for 45-55 minutes, until a toothpick comes out clean.

Let the bread cool in the pan for about 15 minutes, then transfer to a wire rack to cool completely.