Preheat the oven to 350°F (175°C) and grease two 9-inch round cake pans.
In a bowl, combine flour, baking powder, and salt.
Cream butter and sugar until fluffy, then add eggs and vanilla. Gradually add the dry ingredients and milk, alternating between the two.
Divide the batter evenly into the pans and bake for 25–30 minutes. Let cool completely.
For the buttercream, beat butter until creamy. Add powdered sugar, milk, and vanilla, adjusting consistency as needed.
Apply a crumb coat to the cake and chill. Fill a piping bag with buttercream and use a star tip to pipe rosettes in a spiral pattern over the cake.
Decorate with additional touches, if desired, and serve.