Preheat oven to 350 degrees. Combine bananas, eggs, coconut oil and nut butter in the bowl of a food processor. Process until there are no longer any chunks of banana.
Add coconut flour, cocoa powder, cinnamon, baking powder, baking soda, vanilla and salt. Process until all ingredients are well combined.
Add blueberries and pulse a few times to combine.
Line 12 muffin tin cups with cupcake liners. Alternatively, oil muffin tin cups well with coconut oil.
Spoon batter into each cup until it’s 3/4 full. Bake for 23-27 minutes. Bake time will be longer if you use frozen blueberries. Muffins are done when an inserted fork or toothpick comes out clean.