Preheat the oven to 350°F. 

In a large mixing bowl, cream the butter, granulated sugar, and ½ cup of brown sugar using an electric hand mixer on medium-high speed. 

Once the butter and sugars are thoroughly creamed together, add the bananas, eggs, and vanilla extract. Mix again until the batter is smooth and homogeneous.

Add the flour and baking powder and reduce the electric hand mixer to a low speed. Gently mix in the dry ingredients until fully incorporated with the rest of the batter.

Pour the banana bread batter into a 9x5 inch loaf pan. Stir together the remaining brown sugar and the ground cinnamon. Sprinkle the cinnamon mixture over the top of the batter.

Bake the banana bread for 55 minutes, or until a toothpick can be cleanly removed from the center of the pan.

Slice, serve, and enjoy!