Preheat your oven to 350°F (175°C) and grease a 9×5-inch loaf pan.

In a large mixing bowl, mash the ripe bananas with a fork, then mix in the melted butter.

Add the sugar, beaten egg, and vanilla extract, mixing thoroughly.

In a separate bowl, combine the flour, baking soda, and salt. Gradually add this dry mixture to the wet ingredients, stirring until just combined.

In a small bowl, mix the ground cinnamon and brown sugar together.

Pour half of the banana bread batter into the prepared loaf pan, followed by half of the cinnamon mixture. Repeat with the remaining batter and cinnamon mixture to create a swirl.

Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center comes out clean.

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