Preheat your oven to 350°F (175°C).

Prepare your baking pan by greasing it or lining it with parchment paper.

Mash the ripened bananas until smooth, yielding about 1 ½ to 2 cups.

In a large bowl, mix the melted butter, sugar, and eggs with the mashed bananas until smooth.

In another bowl, whisk the flour, baking soda, salt, and cinnamon together.

Slowly add the dry ingredients to the wet mixture, stirring gently until just combined.

Pour half of the batter into the prepared pan and sprinkle with half of the cinnamon sugar mixture. Add the remaining batter and swirl in the remaining cinnamon sugar.

Bake for 60-65 minutes, checking for doneness around 55 minutes.

Cool in the pan for 10 minutes before transferring to a wire rack.