Heat oven to 350°F. Line 18 muffin cups with baking liners. Coat liners with vegetable cooking spray.
In medium bowl, combine flour, baking powder, and salt. In large bowl, with electric mixer on medium-high, beat butter and sugar until light and fluffy. Add eggs and vanilla, beating to combine. Reduce mixer speed to low, and alternately add flour mixture and milk.
Divide batter among baking liners, and bake 20 to 25 minutes, or until cake tester inserted in center comes out clean. Cool completely.
In large bowl, with electric mixer on high, beat butter until fluffy, about 4 minutes. Gradually add confectioners' sugar until combined. Add milk, a little at a time, until frosting is light and fluffy. Beat in vanilla.