Preheat the oven to 350 degrees F (175 degrees C). Line a muffin pan with paper or foil liners.
Spoon flour into a measuring cup and level off with a knife. Sift flour, cocoa, baking powder, baking soda, and salt into a large bowl.
Beat sugar and butter together in a separate large bowl with an electric mixer until light and fluffy.
Add eggs, one at a time, beating well after each addition. Stir in the vanilla. Add flour mixture in two batches, alternating with milk; mix only until no streaks of flour remain.
Spoon batter into the prepared muffin cups, filling each 1/2 full.
Bake in the preheated oven until a toothpick inserted into the centers comes out clean, 15 to 17 minutes. Remove from the oven and let cool in the pan for a few minutes before transferring to a wire rack to cool completely before serving or frosting.
