Preheat oven to 325F degrees. Spray a 9 inch cake pan with extra virgin olive oil, or just grease it with a thin layer of butter. Dust cocoa powder all over the inside of the pan, tapping to evenly distribute. Cut a round of parchment paper and line the bottom of the pan, then spray the parchment lightly. Drain and rinse beans in a strainer. Shake off excess water. Place beans, 3 of the eggs, vanilla, stevia extract, and salt into blender. Blend on high until beans are completely liquified. No lumps! Whisk together cocoa powder, baking powder, and baking soda. Beat butter with sweetener until light and fluffy.