Preheat your oven to 350°F (175°C) and grease a 4×8 inch loaf pan.

In a mixing bowl, mash the ripe bananas with a fork until smooth.

Mix in the melted butter.

Stir in the baking soda and salt.

Mix in the sugar, egg, and vanilla extract.

Finally, stir in the flour until just combined.

In a small bowl, combine cinnamon and brown sugar for the swirl.

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

Use a knife to swirl the mixtures together slightly.

Bake for 60-65 minutes, or until a toothpick inserted into the center comes out clean.

Let it cool in the pan for 10 minutes before transferring to a wire rack.