Preheat your oven to 350°F (175°C) and prepare a loaf pan by lining it with parchment paper.

In a large mixing bowl, mash the overripe bananas until smooth and creamy.

Add melted butter to the mashed bananas and stir until fully incorporated, then beat in the eggs and a splash of vanilla extract.

In a separate bowl, whisk together flour, baking soda, salt, and cinnamon.

Gradually fold the dry ingredients into the wet mixture, stirring just until no floury bits remain.

In a small bowl, combine sugar and cinnamon to create the swirl mixture.

Pour half of the batter into the loaf pan, sprinkle half of the cinnamon-sugar mixture, and layer with the remaining batter and the rest of the cinnamon mixture.

Bake in the preheated oven for 60 to 65 minutes, checking for doneness with a toothpick.

Allow the bread to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.