Instructions: Preheat the oven to 350 degrees. Coat a 9- by 13-inch baking dish with nonstick cooking spray, and flour lightly.

In a large bowl, combine the flour, granulated sugar, baking soda, cocoa, mayonnaise, water, and 1 teaspoon vanilla extract; blend with an electric beater on medium speed until well combined.

Pour the batter into the baking dish. Bake for 25 to 30 minutes, or until a wooden toothpick inserted in the center comes out clean. Let cool completely.

Meanwhile, in a medium bowl, beat the butter until creamy. Add the confectioners sugar, milk, and the remaining 1/2 teaspoon vanilla extract; blend until smooth. Frost cooled cake.

This recipe yields 10 to 12 servings.

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