01 - Preheat oven to 350°F. Line a 12-cup muffin pan with cupcake liners.
02 - In a medium bowl, whisk together the flour, baking powder, and salt.
03 - In a large bowl, beat the softened butter and sugar together until light and fluffy, about 2 minutes.
04 - Add eggs one at a time, beating well after each addition. Mix in the vanilla extract.
05 - Alternately add the flour mixture and the milk to the wet ingredients, beginning and ending with flour. Mix until just combined. Do not overmix.
06 - Divide the batter evenly among the cupcake liners, filling each about two-thirds full.
07 - Bake for 16-18 minutes, or until a toothpick inserted into the center comes out clean.
08 - Remove from oven and let cupcakes cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
09 - Beat the butter until creamy. Gradually add the confectioners' sugar, mixing well. Add vanilla, milk, and salt; beat until smooth and fluffy.
10 - Once cupcakes are completely cool, frost as desired using a piping bag or offset spatula.