'3 1/3 cups of wheat flour'
'1/2 cup of cocoa powder'
'2 teaspoons baking soda'
'1/2 teaspoon salt'
'1 1/2 cups of sugar'
'1/2 cup of low-fat plain yogurt'
'2 egg whites'
'1 tablespoon vanilla extract'
'1 tablespoon white vinegar'
'2 cups of water'
'2 tablespoons confectioner's sugar'
'3 1/3 cups of wheat flour'
'1/2 cup of cocoa powder'
'2 teaspoons baking soda'
'1/2 teaspoon salt'
'1 1/2 cups of sugar'
'1/2 cup of low-fat plain yogurt'
'2 egg whites'
'1 tablespoon vanilla extract'
'1 tablespoon white vinegar'
'2 cups of water'
'2 tablespoons confectioner's sugar'
'Grease a rectangular baking dish with butter.'
'Sift together the flour, cocoa powder, baking soda, and salt in a bowl.'
'In another bowl, beat the sugar, yogurt, egg whites, vanilla extract, and vinegar for 2 minutes on medium speed.'
'Gradually add the dry ingredients to the wet mixture, alternating with water.'
'Bake in a preheated oven for 40 minutes.'
'Dust with confectioner's sugar.'