Preheat your oven to 350°F (175°C) and grease and flour two 9-inch round cake pans.In a large mixing bowl, sift together the flour, cocoa powder, sugar, baking powder, baking soda, and salt until well combined.In a separate mixing bowl, whisk together the buttermilk, vegetable oil, eggs, and vanilla extract until well combined.Gradually add the wet ingredients to the dry ingredients, mixing until just combined. Be careful not to overmix.Stir in the boiling water, mixing until the batter is smooth. The batter will be thin, but that's okay.Divide the batter equally between the prepared cake pans and smooth the tops with a spatula.Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center of the cakes comes out clean.Remove the cakes from the oven and let them cool in the pans for 10 minutes. Then transfer the cakes to a wire rack to cool completely.Once the cakes are completely cooled, you can frost and decorate them as desired. Enjoy your delicious chocolate cake!