Mocha Wacky Cake

Adjust oven rack to middle position and preheat oven to 350°F. Grease 9- by 9-inch cake pan with butter.

Place flour, cocoa, brown sugar, granulated sugar, instant coffee, baking soda, and salt in pan. Stir until completely combined. Make a 4-inch crater in the center of the flour mixture.

Pour the oil, vinegar, and vanilla into the crater.

Pour water over the top. Stir to completely combine (there still may be a few small lumps). Wipe inside edge of extra flour/batter.

Bake until center is just firm, 25 to 30 minutes. Cool completely on wire rack, 2 to 3 hours. Dust with confectioners' sugar and serve.