Preheat your oven to 350°F (175°C).

In a large mixing bowl, whisk together the melted butter, brown sugar, and granulated sugar until smooth and creamy.

Add the sour cream and eggs, mixing well after each addition. Stir in the vanilla extract.

Mash the ripe bananas in a separate bowl until smooth, then stir into the wet mixture.

Sprinkle the flour, baking soda, baking powder, salt, and ground cinnamon over the wet mixture. Gently fold until no dry flour remains.

Grease a 9-inch loaf pan with butter or line it with parchment paper.

Pour the batter into the prepared pan and bake for 45-55 minutes, checking for doneness with a toothpick.

Once baked, let the bread cool in the pan for 10-15 minutes before transferring to a wire rack.