Step 1: Preheat your oven to 350°F (175°C) and line a 12-cup muffin tin with paper liners.
Step 2: In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.
Step 3: In a large bowl, using an electric mixer, cream together the softened butter and granulated sugar until light and fluffy, about 2-3 minutes.
Step 4: Beat in the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Step 5: Gradually add the dry ingredients to the wet ingredients, alternating with the whole milk, beginning and ending with the dry ingredients. Mix on low speed until just combined, being careful not to overmix.
Step 6: Divide the batter evenly among the 12 cupcake liners, filling each about two-thirds full.
Step 7: Bake for 18-22 minutes, or until a toothpick inserted into the center of a cupcake comes out with a few moist crumbs (not wet batter). Let the cupcakes cool in the muffin tin for 5 minutes before transferring them to a wire rack to cool completely.
Step 8: While cupcakes cool, prepare the buttercream: In a large bowl, beat softened butter with an electric mixer until creamy. Gradually add powdered sugar, one cup at a time, mixing until smooth. Add milk or heavy cream, vanilla extract, and a pinch of salt. Beat on high speed until light and fluffy, adding more milk if needed for desired consistency.
Step 9: Once cupcakes are completely cool, frost them with the vanilla buttercream using a knife or piping bag. Enjoy!