Preheat the oven to 350°F. Grease four 6-inch cake pans with baking spray, then dust with black cocoa powder and add parchment paper rounds to prevent any sticking.
In a large mixing bowl, sift in 2 cups of all purpose flour, 1.5 cups of white sugar, ¾ cup of black cocoa powder, 1 teaspoon of salt, 2 teaspoons of baking powder, and 1 teaspoon of baking soda. Use a whisk to make sure everything is evenly dispersed. Set aside.
In a separate large bowl, add the eggs, ⅔ cup of avocado oil, 1 cup of buttermilk, 1 tablespoon of vanilla extract, and 2 teaspoons of distilled white vinegar. Whisk the mixture until completely combined.
Slowly add the wet ingredients to the dry ingredients. We like to add about ⅓ of the wet ingredients at a time until completely combined. Mix the batter until smooth on low speed, but not much more than that. Be sure to scrape the sides to ensure everything is incorporated.
Pour in the ½ cup of hot espresso or strong coffee while whisking to prevent cooking the eggs in the batter. Continue mixing until completely combined and smooth. The batter will be quite wet. Add the batter to the prepared cake tins and try to separate out the batter as evenly as possible, using a food scale for the most precise results.
Place the cake pans on a baking sheet so that you can easily get them in and out of the oven, and bake for 35-40 minutes until a toothpick comes out mostly clean. Allow to cool in the tins for about 15 minutes, then transfer to a cooling rack to cool completely before frosting.