Preheat oven to 350°F. Grease a 9x13-inch baking pan with butter or cooking spray.
In a medium bowl, whisk together the flour, baking soda, baking powder, and salt. Set aside.
In a large bowl, beat together the butter and sugar until light and fluffy. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract, mashed bananas, and buttermilk.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Fold in the chopped walnuts.
Pour the batter into the prepared baking pan and spread evenly. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Cool completely before frosting with your favorite cream cheese frosting.
Interesting Facts
This cake is perfect for using up ripe bananas.
You can add other mix-ins to the cake batter such as chocolate chips, nuts, or dried fruit.
This cake is best served the same day it’s made, but can be stored in an airtight container for up to 3 days.