Preheat the oven to 325 and butter loaf pan(s).
Beat butter and sugar together on medium speed until light and fluffy. Scrape down the bowl several times.
Add the eggs one at a time and mix completely before adding the next egg.
Scrape down the bowl again and add the bananas.
Gently mix in the dry ingredients.
Add the vanilla.
Pour mixture into a large loaf pan and fill ¾. If you have medium loaf pans, divide mixture between pans and be sure to fill ¾.
Bake for 45 minutes until the toothpick comes out of center clean.