Preheat oven to 350ᵒF.

Line the bottom of two 9” round cake pans with parchment paper and oil sides
with baking spray.

In a large bowl with hand/stand mixer on medium speed beat together; butter,
sugar, salt, baking soda, cocoa powder, and vanilla till smooth.

Beat eggs in one at a time, making sure all ingredients are well combined.

In a separate small bowl, mix buttermilk, vinegar, and food coloring till
completely combined.

On low speed, alternate adding cake flour and vinegar to butter and sugar
mixture a little at a time, till all the ingredients are added together and
completely combined.

Once all the ingredients are combined completely, pour cake batter into baking
pans 2/3 full, leaving room for the cake to rise.

Cook in preheated oven for 35-45 minutes, or till toothpick check comes out
“clean”.

When cakes are cooked completely, remove from oven and let cool on wire
rack till at room temperature.

Remove from pans and start assembling cake as desired.

Put one layer of icing between cake layers, and then ice the rest of the cake as
usual.

See “Cream Cheese Frosting” recipe for frosting Red Velvet cake, or use your
own.

I recommend doing a crumb coating first and then apply a thick layer of icing regardless which type of icing/frosting you are using. 

I have also used a Mirror Glaze on this cake, which my daughter says is good, but not as good as the Cream Cheese Frosting.