Preheat the oven to 350°F.
Grease a 9x5-inch loaf pan and set aside.
Add the ripe bananas to a large mixing bowl and mix until smooth.
Add the melted butter, granulated sugar, egg, and vanilla extract to the bananas. Mix until well combined.
Add the flour, baking soda, and salt. Gently mix until just combined, being careful not to overmix the batter.
If using chocolate chips, gently fold them into the batter.
In a small bowl, combine the brown sugar and cinnamon.
Stir until evenly mixed.
Pour half of the banana bread batter into the prepared loaf pan and spread it into an even layer.
Sprinkle half of the cinnamon brown sugar mixture evenly over the batter.
Pour the remaining banana bread batter on top and gently spread it out.
Sprinkle the remaining cinnamon brown sugar mixture over the top.
Using a butter knife, gently swirl the cinnamon brown sugar mixture through the batter.
Bake at 350°F for 60–65 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
If the top begins browning too quickly before the center is finished, loosely tent the loaf with aluminum foil for the remaining baking time.
Remove the banana bread from the oven and allow it to cool in the pan for 10 minutes.
Carefully remove the loaf from the pan and transfer it to a wire rack to cool completely.
Slice and enjoy!