Preheat your oven to 350°F (175°C) and grease a 9x5-inch loaf pan thoroughly.

In a large mixing bowl, mash several ripe bananas until smooth. Then, add granulated sugar, brown sugar, melted unsalted butter, beaten large eggs, and pure vanilla extract. Stir until well-combined and creamy.

Sprinkle in baking soda and a pinch of salt into your banana mixture, then gently fold in all-purpose flour. Mix until just combined, avoiding overmixing.

In a small bowl, combine granulated sugar with ground cinnamon for the swirl. Mix until evenly combined.

Pour half of your banana bread batter into the greased loaf pan, spreading it evenly. Sprinkle half of the cinnamon sugar mixture over this layer. Pour the remaining batter on top, followed by the rest of the cinnamon mixture.

Gently swirl through the layers of batter with a butter knife or skewer to create a marbled effect.

Place the loaf pan in the preheated oven and bake for 50-60 minutes. It's done when a toothpick comes out clean.

Once baked, let the bread cool in the pan for about 10-15 minutes before transferring it to a wire rack.

Prepare the glaze by whisking together powdered sugar and milk until smooth. Adjust consistency as needed.

Drizzle the glaze over the cooled bread and allow it to set before slicing.