Position rack in the center of the oven and preheat to 325 degrees F. Oil and flour an 8-inch square cake pan.Advertisement
Sift together sugar, flour, cocoa, baking soda and salt into a large mixing bowl. Whisk together egg, oil and vanilla in a small bowl. Stir lemon juice into milk. Add to the egg mixture. Stir in hot water. Add the wet ingredients to the dry ingredients and stir until smooth.
Turn batter out into the prepared pan. Bake until center springs back when pressed lightly and a toothpick inserted in the center comes out clean, 30 to 35 minutes. Cool the cake upright on a wire rack for 10 minutes. Run a knife around the sides of the pan to loosen. Invert onto the rack, lift off pan and let cool completely. Place on a serving dish. Top with a light dusting of confectioners' sugar if desired.
1/2 starch, 1 other carbohydrate