Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan.
In a medium bowl, combine flour, baking soda, baking powder and salt. In a large bowl, cream together the melted butter and sugar until smooth. Beat in the eggs one at a time, then stir in the vanilla. Beat in the flour mixture alternately with the mashed bananas. Fold in the chopped walnuts if desired. Spread evenly into the prepared pan.
Bake for 30 to 40 minutes in the preheated oven, or until a toothpick inserted into the center of the cake comes out clean.
Interesting Facts
Banana cake is a popular dessert in many cultures.
Bananas are a great source of potassium and fiber.
This cake is a great way to use up overripe bananas.