1. Combine flour, cocoa, baking powder and salt in large bowl. In another bowl, whisk sugar, liquid egg whites, oil and vanilla until creamy. Add egg mixture to dry ingredients, stirring just until blended.
2. Pour into greased 8” (20 cm) square pan. Bake at 350°F 20-25 minutes or until firm to the touch (do not overbake). Cool and cut into squares. Store in refrigerator.