Preheat oven to 356F and prepare two 6-inch cake pans.
Melt the butter (about 20 seconds in the microwave).
Add the ripe bananas, eggs, raisins, and melted butter to a blender and blend until smooth.
Combine the oat flour, all-purpose flour, baking powder, and cinnamon in a medium bowl.
Whisk the dry ingredients until combined.
Pour the blended wet ingredients into the dry ingredients bowl and whisk until combined.
Split the cake batter evenly into the two 6-inch cake pans. Bake for 25 minutes or until a toothpick comes out clean. Allow the cake to cool before removing from the cake pan.
In the meantime, prepare the frosting of choice (see options below in the recipe notes).