Preheat your oven to 350°F (175°C). This ensures that the bread bakes evenly and rises properly.

Grease a 9x5 inch loaf pan with butter or non-stick spray to prevent sticking.

In a large mixing bowl, mash the ripe bananas with a fork until smooth. This adds moisture and sweetness to the bread.

Stir in the melted butter until well combined.

Add the egg and vanilla extract, mixing until fully incorporated.

In a separate bowl, whisk together the flour, baking soda, salt, granulated sugar, and brown sugar.

Gradually add the dry ingredients to the banana mixture, stirring gently with a rubber spatula until just combined. Be careful not to overmix, as this can lead to a dense bread.

In a small bowl, mix together the ground cinnamon and granulated sugar. This will create the swirl that adds flavor and sweetness.

Pour half of the banana bread batter into the prepared loaf pan, spreading it evenly.

Sprinkle half of the cinnamon sugar mixture over the batter.

Pour the remaining batter on top and spread it evenly. Finally, sprinkle the remaining cinnamon sugar mixture on top.

Using a knife or a skewer, gently swirl the batter and cinnamon sugar together to create a marbled effect. This will ensure the cinnamon flavor is distributed throughout the bread.

Place the loaf pan in the preheated oven and bake for 55-60 minutes, or until a toothpick inserted into the center comes out clean. The baking time may vary depending on your oven.

Once baked, remove the bread from the oven and let it cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.