Preheat your oven to 350°F (175°C).

Grease and flour two 9-inch round cake pans.

In a large mixing bowl, combine the all-purpose flour, granulated sugar, cocoa powder, baking soda, baking powder, and salt.

Add in the mayonnaise, water (or coffee), and vanilla extract. Beat on medium speed for about 2 minutes until fully incorporated.

Pour the batter evenly into the prepared cake pans.

Bake for 30 to 35 minutes or until a toothpick inserted in the middle comes out clean.

Let the cakes cool in the pans for about 10 minutes, then transfer to a wire rack to cool completely.

While the cake is cooling, whip up your frosting. In a chilled bowl, beat the heavy cream, powdered sugar, and vanilla extract until soft peaks form.

Place one cake layer on a serving plate, spread a generous layer of whipped cream, then top with the second layer.

Finish by frosting the top and sides as desired.

Slice, serve, and enjoy!