Preheat the oven to 350°F. Spray a 9x13 baking dish with non-stick cooking spray.
In a large bowl, mix together the devils food cake mix, eggs, milk and mayonnaise.
Pour the batter into the baking dish. Bake for 35-38 minutes, until a toothpick comes out clean when poked in the center. Let the cake cool completely.
Once cake is cooled, spread the frosting on top with a knife or a spatula.