Preheat oven to 325 degrees F. Spray a 9 inch cake pan with coconut oil cooking spray. Dust the inside of the pan with cocoa powder.
Drain and rinse beans in a colander.
Add beans, 3 eggs, vanilla, stevia and salt into blender or VitaMix. Blend on high until beans are completely liquefied and smooth throughout.
In a medium bowl, whisk together cocoa powder, baking soda, and baking powder.
In another bowl add the coconut oil and erythritol and beat with an electric mixer until fluffy.
Add remaining eggs to the coconut oil/erythritol mixture, beating for one minute after each addition.
Pour bean batter into egg mixture and mix to combine.
Stir in cocoa powder and water and beat the batter on high for one minute, until smooth.
Pour batter into pan and shake gently to evenly distribute.
Transfer to the oven and bake for 40-45 minutes or when firm to the touch.
Cool and serve.