Preheat your oven to 350 °F. Prepare a 9 inch square baking pan by lining it with parchment or a silicone mat..
Mix the batter by adding all of the ingredients to a food processor and processing until smooth. Alternatively, if you don't have a food processor, you can mash the bananas until smooth in a large bowl. Add the nut butter and cocoa and mix until well combined.
Pour brownie batter into the baking pan and use a spatula to smooth into an even layer. Bake for 17-22 minutes until they appear set on top.
Allow to cool in the pan for 15 minutes. Cut and move to a wire rack to cool completely (or enjoy warm!).
Notes
LeftoversStore leftovers in an airtight container in the refrigerator for up to 4 days or freeze for up to 3 months.