Preheat oven to 350 F. Line a 12 cup muffin pan with cupcake liners. In a medium bowl, whisk together flour, salt and baking powder.
In a large bowl using either a hand or stand mixer, beat softened butter with sugar until fluffy. Add in eggs, milk and vanilla extract. Beat until smooth.
Add flour mixture in two additions, beating well after each addition until fully combined. Evenly fill cupcake liners 2/3 full. Bake for 20-25 minutes.
For the buttercream frosting, in a large bowl using either a hand or stand mixer beat softened butter with powered sugar until fluffy. Add in vanilla extract and milk as needed to thin the frosting. Beat until desired consistency.
Pipe frosting onto cooled cupcakes.