Preheat your oven to 350°F (175°C) and prepare a 9-inch bread pan by greasing it or lining with parchment paper.

In a large bowl, combine melted butter, brown sugar, and granulated sugar. Whisk until smooth, about 2 minutes. Add sour cream, then eggs one at a time, whisking to combine.

Mash the ripe bananas until smooth and fold them into the wet mixture along with the vanilla extract.

In another bowl, whisk together flour, baking soda, baking powder, salt, and cinnamon. Gradually fold into the wet ingredients until just combined.

Pour the batter into the prepared pan and bake for 45-55 minutes, checking for doneness at 40 minutes.

Let the banana bread cool in the pan for 10-15 minutes, then transfer to a wire rack to cool completely.