Preheat oven to 350°F. Grease a 9-inch round cake pan with coconut oil and line the bottom with unbleached parchment paper.
Place all ingredients (except optional add-ins) in a Vitamix and blend until completely smooth and well combined. Stir in chocolate chips if using.
Pour batter evenly into prepared cake pan. Arrange banana slices on top of cake and bake for 25 to 35 minutes until just set and a toothpick comes out clean or with dry crumbs. Cool for a few minutes before removing from pan and allowing to cool completely on a cooling rack.