Preheat the oven to 350°F. Spray the inside of an 8 x 8 inch pan with nonstick cooking spray.
Take one of the nectarines and dice it, set it aside. Take the other nectarine and cut it into slices, and set it aside separately.
In a large bowl, add the almond flour, tapioca flour, coconut flour, cinnamon, baking soda, and salt. Mix with a fork until combined.
In another bowl, whisk the olive oil and the coconut sugar until well mixed. Add the eggs and whisk. Add the almond milk and vanilla, and whisk again. Then, add the mashed bananas to the mixture and mix. Add the flour mixture to the wet banana mixture and mix well. Fold in the diced nectarines.
Pour the batter into the 8 x 8 pan, and smooth the top with a spatula. Top with the nectarine slices ( make a pretty design or just place them evenly on top).
Bake the cake in the oven until the top of the cake is caramelized brown and a tooth pick comes out clean, about 40-45 minutes.