01 - Preheat the oven to 350°F. Grease and line two 9-inch round cake pans with parchment paper.
02 - In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
03 - In a large bowl, beat butter and sugar with an electric mixer until light and fluffy, about 3-4 minutes.
04 - Add eggs one at a time, beating well after each addition. Mix in vanilla extract.
05 - Alternately add the flour mixture and milk to the butter mixture, starting and ending with flour. Mix until just combined; do not overmix.
06 - Divide batter evenly between prepared pans. Smooth the tops with a spatula.
07 - Bake for 28-32 minutes, or until a toothpick inserted into the center comes out clean.
08 - Let cakes cool in pans for 10 minutes, then turn out onto wire racks to cool completely.
09 - Beat butter until creamy. Gradually add powdered sugar, milk, vanilla extract, and salt; beat until smooth and fluffy, about 3 minutes.
10 - Once cakes are completely cool, spread a layer of buttercream between the layers. Frost the top and sides with remaining buttercream.