What you see here is the bottom of a cupcake silicone mold from Fred and Friends. Genius, I tell you; not only do you get to eat delicious cake, but you get that sense of accomplishment that only discovering dinosaur bones can give!
2 C all purpose flour1 1/4 C sugar3/4 tsp baking soda3/4 C dutch-processed cocoa powder1 1/4 C water1 C mayo1 Tbsp vanilla extractConfectioners' sugar (for serving; optional)
Adjust an oven rack to the middle position and heat the oven to 350 degrees. Lightly coat an 8" square cake pan with vegetable oil spray.
Whisk the flour, sugar, and baking soda together in a large bowl. In a separate bowl, whisk the cocoa and water together until smooth. Whisk in the mayo and vanilla. Stir the mayo mixture into the flour mixture until combined.
Scrape the batter into the prepared pan and smooth the top. Bake until a wooden skewer inserted into the center of the cake comes out with a few crumbs attached, 35 to 40 minutes.
Let the cake cool in the pan on a wire rack, 1 to 2 hours. Cut into squares and serve straight from the pan.
Serves 9, from America's Test Kitchen Family Cookbook