Preheat oven to 350°F. Line muffin tin with cupcake wrappers. Set aside.
In a large bowl, whisk together flour, cocoa powder, sugar, baking soda, baking powder, and salt.
Add buttermilk, water, eggs, oil, and vanilla to bowl. Using a spatula, stir to combine until all dry ingredients are moistened. Mix until thoroughly combined.
Fill prepared muffin ⅔ full with batter. Bake for 20-22 minutes, rotating pan midway through baking. Bake until toothpick inserted in center of cupcake comes out clean. Let cupcakes cool on wire rack until room temperature.