Preheat your oven to 350° F and spray two 8” pans with baking spray or line the bottoms with parchment paper.
In a medium sized bowl whisk together the 2 1/4 cup flour, 1/4 cup cocoa, 1 tsp salt, and 1 tsp baking soda. Set aside. In the bowl of a mixer fitted with the paddle attachment combine the 1 cup oil, 2 cups sugar, 2 eggs, and 1 yolk. Mix on medium speed until light and pale yellow, about 1 minute.
Add the 1 tsp vanilla extract and 2 tbsp food coloring and mix again for 30 seconds. Alternate adding the flour mixture with the buttermilk. First add ⅓ the amount of flour to the batter and mix on low- medium speed till combined. Then add in half of the buttermilk. Mix, add in ⅓ more of the flour, mix. Add in the other half of the buttermilk, mix, and then add in the remaining flour mixture.
Continuing mixing on low - medium speed until an even batter forms. Add in the 2 tsp white vinegar and mix once more about 30 seconds.
Pour the batter into the pans and check for doneness after 30 mins. The cake is done when it starts coming off the sides of the pan or if a toothpick inserted in the middle comes out clean.
Make the cream cheese frosting
You will need to clean your mixing bowl. In the bowl of a mixer fitted with the paddle attachment add the 3 1/2 cups confectioners sugar, 8 oz cream cheese, and 1/2 cup butter. Beat on medium speed till fluffy. Add the 1 tsp vanilla extract and 1 tsp heavy cream and mix again till stiff peaks form. When the cake has cooled, fill and frost with the cream cheese icing.
Notes
If you don't have buttermilk you can easily make your own. Fill up a measuring cup with 1 cup of milk. Take out one tablespoon and replace it with a tablespoon of lemon juice. Let it sit for 5 minutes. Voila! You now have your own buttermilk.
This cake is best made dairy but you can sub it with a non dairy milk substitution of your choice.
The cream cheese frosting doubles well if you want an extra thick layer.
You can make this into 3 layers and in 9" baking pans just make sure you check the cakes after 25 minutes instead of 30 minutes.
You can make this cake into cupcakes, bake them at 350 for 18 minutes!