Grease a 9x9x2-inch baking pan. Line the bottom of pan with waxed paper; grease the paper and flour the pan. Set aside.
In a large bowl, combine all-purpose flour, sugar, cocoa powder, baking soda, and salt. Add hot water, olive oil, vanilla and cider vinegar. Beat with an electric mixer on low speed until combined. Beat on medium speed for 1 minute. (Do not over mix.) Spread batter in the prepared pan.
Bake in a 375 degrees oven for 20 to 25 minutes or until a wooden toothpick inserted near the center comes out clean. Cool in pan on a wire rack for 10 minutes. Remove layer from pan; peel off waxed paper.