1. Preheat the oven to 350 F and line an 8×8 baking pan with parchment paper, leaving a bit of overhang on the sides. In a large mixing bowl, mash the bananas until nearly liquid, with no large lumps remaining. Add the eggs and whisk thoroughly. Add in the yogurt, avocado oil, maple syrup and vanilla and combine. Set aside.
2. In another large bowl, sift together the almond flour with the gluten free flour. Add in the baking powder, baking soda, cinnamon and salt. Add the dry ingredients to the wet ingredients and stir gently with a large wooden spoon. If you’re using the chocolate chips, add them now and gently stir them into the batter. 
3. Pour the batter into the prepared cake pan and place the cake in the oven to bake for 26-27 minutes, or until a toothpick inserted in the center comes out clean. Remove the cake from the oven and allow it to cool completely before grabbing the sides of the parchment, and lifting the cake out of the pan and on to a cooling rack. Cut and serve, or make the frosting.
4. Make the frosting. In the bowl of a stand mixer fitted with the paddle attachment, beat the dairy free butter until smooth, before adding in the powdered sugar, cinnamon and vanilla extract. Add the dairy free milk, a little at a time, until a smooth consistency is met. Frost the cooled cake and serve immediately.

Leftover cake can be stored at room temperature for a day or two, but then should be refrigerated or frozen any longer than that. It can be frozen for up to 2 months.