Preheat oven to 350°F (175°C) and grease a 9-inch springform pan.
In a bowl, whisk flour, cocoa powder, baking powder, and salt.
In a separate bowl, beat butter and sugar until light and fluffy.
Add eggs one at a time, mixing well after each.
Stir in vanilla and milk, then gradually mix in dry ingredients.
Spread batter evenly in the prepared pan.