Preheat the oven to 350°F and line a muffin tin with cupcake liners.
In a large bowl, whisk together flour, sugar, cocoa, baking powder, baking soda, and salt.
In another bowl, whisk the oil, eggs, and vanilla until smooth.
Add the wet ingredients to the dry and stir gently.
Pour in the buttermilk and hot water, mix until the batter is smooth.
Divide the batter evenly among the liners, filling each about two-thirds full.
Bake for 18 to 20 minutes, or until a toothpick comes out clean.
Let the cupcakes cool before frosting with your favorite icing.