Preheat oven to 350°F and line a cupcake pan with liners.
In a bowl, whisk together flour, cocoa powder, baking soda, and salt.
In a separate bowl, whisk sugar, sour cream, coffee, oil, egg, and vanilla until smooth.
Add dry ingredients to wet and mix until just combined.
Divide batter evenly among liners and bake for 18–20 minutes.
Let cool completely before frosting.