Preheat the oven to 350°F and grease and line two 8-inch round cake pans with parchment paper.
Beat the egg whites until soft peaks form. Add 2 Tablespoons of sugar to the egg whites and beat on high power. Add another 2 tablespoons of sugar and beat again until fully incorporated and stiff peaks form. Set this aside
In a large mixing bowl beat the remaining sugar with the flour, buttermilk, vegetable oil, baking powder, salt, and vanilla at low speed until combined.
Divide the batter into 2 bowls. In one bowl, beat in half of the egg whites.
In the other bowl, beat in cocoa and 2 Tablespoons granulated sugar. Then, beat in the other half of the egg whites.
Spoon half of the vanilla cake batter into each of the pans. Then drop spoonfuls of half of the chocolate cake batter into each pan on top of the vanilla batter.
Drag a butter knife through the batter to swirl the batter flavors together but do not fully mix.
Bake for 25 minutes or until a toothpick inserted into the cetner comes out clean. Remove and allow the cakes to cool in the pans on wire racks before flipping them out.
While the cakes are cooling, prepare the Chocolate Frosting recipe.
Place one cake on a plate or cake stand and top with chocolate frosting, then add the second cake and add a crumb coat of frosting. Place the cake in the refrigerator for about 20 minutes then finish by frosting the top and edges of the cake with a nice thick layer.