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

In a large mixing bowl, melt the unsalted butter, then whisk in the granulated sugar, eggs, and vanilla extract until smooth.

Gently fold in the mashed ripe bananas into the wet mixture.

In another bowl, whisk together the all-purpose flour and baking soda, then gradually stir this dry mixture into your banana mixture until combined.

For the cinnamon swirl, mix melted butter, granulated sugar, dark brown sugar, and ground cinnamon in a small bowl until thick.

Layer a quarter of the batter into the pan, add dollops of the cinnamon mixture, and use a knife to swirl it in. Repeat until all the batter is used.

Place sliced bananas on top before baking. Bake for 60-70 minutes or until a toothpick comes out clean.

Allow the bread to cool in the pan for 30 minutes before transferring to a wire rack to cool completely.