Preheat the oven to 350ºF. Grease two (8-inch) round cake pans. Line them with parchment paper, then grease and flour the parchment paper. This helps the cakes release from the pans later.
Combine the unsweetened almond milk and the vinegar in a measuring cup or small bowl. Set aside. The milk will start to slightly curdle but will not get as thick as buttermilk. Let it sit until is time to use it.
Meanwhile, in the bowl of a stand mixer fitted with the paddle attachment or in a large bowl if using a handheld mixer, whisk together the flour, sugar, cocoa powder, baking powder, baking soda and salt.
With the mixer on low speed, add the oil, apple sauce vanilla and buttermilk mixture and mix on medium speed until well combined, scraping down the sides and up the bottom of the bowl with a rubber spatula as needed.
With the mixer on low speed, slowly and carefully pour in the hot coffee or hot water. At this point, the cake batter will look thin and runny.
Pour the batter into the prepared cake pans, dividing the batter evenly.
Bake for 30-40 minutes, or until a toothpick cake tester inserted in the middle of the cake comes out clean. Cool in the pans for 10 minutes and then remove the cakes from the pans and turn them onto a cooling rack to cool completely before frosting.