1 teaspoon cider vinegar
Powdered sugar, for dusting (optional)
Preheat the oven to 350°F. Whisk together the cocoa powder, flour, granulated sugar, salt, baking soda, and baking powder in a 9-inch square cake pan.
Add the water, oil, and vinegar to the pan, stirring gently to blend the wet ingredients into the dry. Scrape down the sides with a silicone spatula and bake until a cake tester inserted in the center comes out clean, about 30 minutes. Cool for 30 minutes before serving. Serve plain or dusted with powdered sugar.
Reprinted with permission from The Homemade Kitchen: Recipes for Cooking with Pleasure by Alana Chernila, copyright (c) 2015. Published by Clarkson Potter/Publishers, an imprint of Penguin Random House LLC.