Position the rack in the center of the oven and preheat oven to 350°F.
Whisk the cocoa powder, sugar, flour, baking powder and salt in a large bowl. Then use a wooden spoon to stir in the yogurt and vanilla until smooth but quite thick.
Coat an 8-inch square baking pan with cooking spray. Spread the thick batter into the pan, evenly to the corners.
Bake until a toothpick inserted into the center of the cake comes out with a few moist crumbs attached, about 20 minutes. Cool on a wire rack for 15 minutes before cutting into 16 squares, 2- X 2-inches each. Yields 1 square per serving.
I needed to add a little more yogurt and an egg white. At first the consistency was more dough like. The extra yogurt and egg(white) made it more like a heavy frosting. I would like to toy with this some more. Feel free to do the same and let me know what you did and how it goes.
The brownies themselves are quite tasty. I ate two. But I stopped at two.