Preheat the oven to 350 degrees F and spray two 8-inch round cake pans with oil. I also line them with a circle of parchment paper for easy removal.
Measure 1 cup of soy milk and add the tablespoon of apple cider vinegar to it. Stir and set aside to curdle.
In a large bowl (I use my stand mixer with whisk attachment), add the flour, sugar, cocoa powder, baking powder, baking soda and salt. Whisk well to combine.
To the bowl with the dry ingredients, add the oil, applesauce, vanilla and milk/vinegar mixture. Mix on medium speed, either with a hand mixer or a stand mixer, until well combined. Scrape down the sides as needed.
Lower the speed and slowly pour in the boiling hot water, continuing to mix until combined. The batter will seem runny, which is correct.
Divide the batter evenly between the pans and bake for 35-37 minutes, or until a toothpick inserted comes out clean. After 10 minutes of cooling in the pans, carefully invert the cakes onto a wire cooling rack to cool completely.