Preheat the oven to 350°F and Line an 8-inch square pan with parchment paper or use coconut oil to grease the pan.
Gather all your ingredients.
In a large bowl mix all the wet ingredients including the drained black beans and bananas. Mash the bananas and some of the beans. You can skip the mashing part if you have a food processor but when using a blender this step makes it easier to get everything smooth.
In a separate bowl, whisk together the cacoa powder, baking powder, baking soda, stevia and sea salt (all the dry ingredients).
Combine everything and add to a blender. Mix until smooth.
Transfer to the pan and spread out evenly.
Place into the oven and bake until the top of the brownie block is firm to the touch, about 30 minutes. Turn oven off and let sit for another 10 minutes before removing.
Once baked, place the pan outside the oven to cool for about 1 hour. Use the parchment to pick up the brownie block and transfer it to a cutting board. Slice into 20 squares; for clean cuts, wipe the knife after each cut and dip in hot water. Store the brownies in an airtight container in a cool place for 3 to 4 days (they can also be frozen).
These vegan brownies taste even better the next day (if they last that long).