Preheat your oven to 350°F (175°C). Grease a 9x5-inch loaf pan well or line it with parchment paper. This helps the bread release easily after baking and makes cleanup much simpler.

Place the ripe bananas in a large mixing bowl. Mash them with a fork until mostly smooth. Small lumps are perfectly fine because they add texture and extra banana flavor to the finished loaf.

Add the melted butter, brown sugar, eggs, and vanilla extract to the mashed bananas. Whisk everything together until smooth and well combined. The mixture should look creamy and evenly blended.

Add the flour, baking soda, salt, and cinnamon. Stir gently with a spatula until no dry flour remains. Avoid overmixing because it can make the bread dense instead of soft and tender.

In a small bowl, combine the brown sugar, cinnamon, and melted butter. Mix until you have a thick paste. This mixture creates the delicious cinnamon roll flavor throughout the bread.

Pour half of the banana bread batter into the prepared loaf pan. Spread it evenly. Spoon half of the cinnamon mixture over the batter and gently swirl it with a butter knife.

Pour the remaining batter over the first layer. Spread it carefully to cover the cinnamon mixture. Add the remaining cinnamon swirl mixture on top and create gentle swirls throughout the batter.

Place the loaf pan in the oven and bake for 50 to 55 minutes. The bread is ready when a toothpick inserted into the center comes out with only a few moist crumbs.

Remove the bread from the oven and let it cool in the pan for 15 minutes. Transfer it to a wire rack and allow it to cool completely before adding the glaze.

Whisk together the powdered sugar, milk, and vanilla extract until smooth. Drizzle the glaze over the cooled bread. Let it set for a few minutes before slicing and serving.