Preheat oven to 350°F
Beat together butter and sugars. Beat for at least 3 minutes. (Don't skip this step, it's very important to the texture)
Add in vanilla and eggs. Beat until combined. Add in bananas.
Add in flour, baking soda, baking powder, salt, & cinnamon. Mix until well combined.
Pour batter into a greased 9x5 loaf pan. Bake for 50-60 minutes, or until toothpick comes out clean.