Preheat oven to 325°F. Spray 2, 9-inch round cake pans with nonstick cooking spray and line each with parchment paper. Set aside.
In a large bowl, whisk together the flour, sugar, baking soda, baking powder, cocoa powder, and salt.
In a separate bowl, whisk together the mayonnaise, eggs, buttermilk, vanilla, red food coloring, hot water, and vinegar.
Slowly add the wet ingredients to the dry ingredients, mixing until just combined.
Divide the batter equally between the prepared pans. Bake for 35-40 minutes, or until a toothpick comes out mostly clean. A few crumbs are what you want for a MOIST cake!
Allow the cakes to cool for 10-15 minutes in the pans. Then, turn the cakes out onto a rack to cool completely. After the cakes have cooled completely, make the frosting.