Grease a 9 inch bread pan with butter, or create a parchment sling and spray with cooking spray. (Full directions in the notes). Preheat the oven to 350 degrees.

In a large mixing bowl, combine the melted butter, brown sugar, and white sugar. Whisk together until smooth, creamy, and no brown sugar lumps remain.

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

In another bowl, mash the bananas then whisk them into the sour cream mixture.

Sprinkle the flour, baking soda, baking powder, salt, and cinnamon on top of the wet ingredients, then stir everything together until no white remains.

Pour the batter into the prepared pan and bake for 45-55 minutes or until a toothpick inserted in the center comes out with just a few moist crumbs. Note: I usually check the bread at the 35 minute mark. If the top is getting too browned, cover it with foil for the remaining baking time. Allow the bread to cool for 15 minutes before removing from the pan. Cool completely on a wire rack, after you sneak a slice warm from the oven, of course.