• This cake requires buttermilk, but a buttermilk substitute works even better thanks to the acidity from the white vinegar. To make buttermilk substitute, add 2 tablespoons of white vinegar into a measuring cup and fill the rest up with milk until it reaches 1 total cup of liquid. Set aside. It will curdle, which is perfectly normal.
• Prepare the loaf pan either with parchment paper or grease with oil and sprinkle some cocoa powder in the pan. Preheat oven to 350℉. Add the vegetable oil and sugar to a large mixing bowl and whisk them together for about 2 minutes. Whisk in the egg and vanilla extract.
• In a medium-sized bowl, sift together the flour, cocoa powder, baking soda, and salt. Take turns alternating adding the dry ingredients to the oil and sugar mixture and the buttermilk, mixing until just combined. I pour half the flour mixture, then half the buttermilk, and then pour in the remaining ingredients from there. Use a rubber spatula to scrape the sides of the bowl.
• Finally, add the red food coloring until it's just mixed in. Be mindful to not overmix the batter. Bake on the middle rack of the oven for 50-60 minutes. The cake will be done when you stick a wooden toothpick in the center of it and it's clean or moist crumbs stick to it. If there is still wet batter, it needs to bake longer. Allow it to cool in the pan for about 10 minutes before guiding it out with a butter knife and allowing it to cool completely on a wire rack.
• If you want to decorate the top of the cake with red velvet cake crumbs, scrape a tiny bit of crumbs off from the bottom of your cake (only about a tablespoon of crumbs is needed). Break the crumbs up and set aside until after you've frosted the cake.

Make the cream cheese frosting:

• To make the cream cheese frosting, cream together the butter and cream cheese with an electric mixer until they are nice and soft (no clumps). Then add the vanilla extract and salt (if using unsalted butter). Finally, mix in the powdered sugar one cup at a time. Use a spatula to scrape the sides of the bowl to incorporate all the powdered sugar. Frost the cake with an offset spatula.