Beat the softened butter and granulated sugar together in a large bowl until light and fluffy.
Add the eggs one at a time, beating well after each addition, then stir in the vanilla extract.
Whisk the flour, baking powder, and salt together, then add to the batter alternately with the milk, mixing until just combined.
Divide the smooth batter evenly among 12 paper-lined muffin cups, filling each about two-thirds full.
Bake at 350°F (175°C) for 18 to 20 minutes until a toothpick inserted into the center comes out clean, then cool completely before frosting and serving.