best banana cake ever

I have tried a LOT of gluten-free banana bread and banana cake recipes looking for the magic combination texture, lightness and taste and with only a few modifications from "Gluten-free Homemaker" I think we have a winner!


1/2 cup butter
1 1/2 cup sugar
2 large eggs
1 cup mashed ripe banana (about 3 large)
1 1/2 teaspoons vanilla
3/4 cup mayonnaise
1/4 cup brown rice flour
1/2 cup sorghum flour
3/4 cup potato starch (not potato flour)
1/2 cup tapioca starch (or tapioca flour)
1 teaspoon xanthan gum
1 teaspoon baking soda
1 teaspoon baking powder
1/2 teaspoon salt

Preheat the oven to 350 and line a 9x13 pan with parchment paper.
Mix the dry ingredients: GF flours & starches, xanthan gum, baking soda, baking powder & salt in a small bowl and set aside. 
Cream the butter and add the sugar, creaming until light. Add in order: eggs, banana, vanilla and finally mayonnaise.
Add the dry ingredients to the butter mixture and beat until well mixed.
Pour into the prepared pan and place in the middle of preheated oven.
Bake for about 40 minutes. Test by inserting a toothpick in the middle and see if it comes out clean.