Preheat the oven to 325 degrees F. Spray a 9" loaf pan with non-stick spray and set aside. (See notes if you don't have a large loaf pan)
Mix the 1/3 cup of milk with 1 tsp of lemon juice or vinegar and let sit while you mix up the batter. (You could also use buttermilk and omit the lemon juice or vinegar)
Take a half a stick of butter (1/4 cup) and melt it in a small bowl and set aside.
In a large mixing bowl, add the flour, baking powder, baking soda, salt, and cinnamon. Whisk well and set aside.
In another bowl, mash the bananas, then add the granulated sugar, brown sugar, oil, melted butter (make sure that it's not super hot), the milk that was mixed with lemon juice or white vinegar, vanilla extract and eggs. Mix well with a whisk.
Pour the liquid mixture into the dry mixture and mix well with a spoon. Do not over-mix. Only mix until all the ingredients are well incorporated. It's okay to leave a few small lumps in it.
Pour the batter into the sprayed loaf pan.
Bake at 325 degrees for approximately 1 hour, 5 minutes for dark coated pans and about 1 hour plus 15-20 minutes for lighter or disposable pans. A toothpick inserted into the center will come out with a few moist crumbs on it or clean, but no liquid batter on it.
Cool the bread in the pan on a cooling rack for about 15 minutes, then turn the bread loaf out of the pan and let cool completely on the rack.
Once cool, wrap with plastic wrap and let sit overnight before serving. (This last step is optional, but it allow the flavors to intensify.)