Preheat your oven to 350°F (175°C) and grease a 9x5-inch loaf pan with butter or non-stick spray.

Melt the unsalted butter in a large mixing bowl and let it cool slightly. Mix in the white sugar until blended, then add in the eggs and vanilla extract, stirring until smooth.

Fold in the mashed ripe bananas into the mixture, ensuring they are well incorporated.

In a separate bowl, whisk together the all-purpose flour and baking soda, then gradually add it to the wet mixture, stirring gently until combined.

In a small bowl, combine the melted butter, white sugar, dark brown sugar, and ground cinnamon until it reaches a thick but spreadable consistency.

Pour a quarter of the banana batter into the greased pan, create dollops of the cinnamon mixture on top, and swirl. Repeat with remaining batter.

Garnish the top with banana slices before baking.

Bake for 60-70 minutes or until golden-brown and a toothpick inserted comes out clean.

Let the banana bread cool in the pan for 30 minutes, then transfer to a wire rack to cool completely before slicing.