Preheat your oven to 350°F (175°C) and line a standard 12-muffin tin with cupcake liners.
In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt until well combined.
In a separate bowl, mix the vegetable oil, eggs, and vanilla extract until blended.
Add the buttermilk to the wet ingredients and stir until smooth.
Gradually add the wet mixture to the dry ingredients, mixing until just combined. Be careful not to overmix!
Slowly stir in the boiling water until the batter is smooth. It’ll be thin, but that’s what makes these cupcakes so moist.
Divide the batter evenly among the cupcake liners, filling each about ⅔ full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove the cupcakes from the oven and let them cool in the pan for about 5 minutes before transferring them to a wire rack to cool completely.