
Preheat your oven to 325°F.
Grease and flour three 8-inch round cake pans, or use baking spray. Set aside.
In a large bowl, sift or whisk together the flour, salt, baking soda, and cocoa powder. Set aside.
In a separate bowl, beat the eggs until smooth.
Add the sugar, buttermilk, oil, and vanilla extract to the eggs. Mix until smooth and creamy.
Gradually add the dry ingredients to the wet mixture. Mix on low speed just until combined. Do not overmix.
Switch to folding the batter gently.
Add the vinegar and red food coloring. Fold until the batter is evenly red and no streaks remain.
Divide the batter evenly between the three prepared 8-inch pans.
Tap the pans gently on the counter to release air bubbles.
Bake at 325°F for 28–33 minutes, or until a toothpick inserted in the center comes out clean. Begin checking at 28 minutes.
Remove the cakes from the oven and allow them to cool in the pans for about 10–15 minutes.
Carefully remove the layers from the pans and transfer them to cooling racks. Let them cool completely before frosting.
In a large mixing bowl, beat the softened cream cheese and butter together until smooth and fluffy.
Gradually add the powdered sugar, one cup at a time, mixing well after each addition.
Add the vanilla extract and milk.
Beat until smooth, creamy, and spreadable.
Place one cake layer on a cake stand or serving plate.
Spread an even layer of frosting on top.
Add the second layer and repeat.
Place the third layer on top and frost the top and sides of the cake.