Preheat oven to 350°F.
In a large bowl combine butter, milk, and sugar.
Add eggs and mashed bananas and mix until combined.
In a separate medium bowl, whisk together flour, baking powder, baking soda, cinnamon, and salt.
Pour the dry mixture into the wet mixture and fold together until just combined.
Pour the mixture into a prepared 9-inch loaf pan.
In a small bowl combine sugar and cinnamon.
Top the loaf with the cinnamon-sugar mixture evenly.
Place into the oven and bake for 1 hour or until done. Place a toothpick into the center of the loaf. If moist crumbs are stuck on the toothpick, it is done. If it comes out with batter, give it an additional few minutes before testing again.