Combine the flour, baking powder and salt in a large bowl. Set aside.
Combine the butter and sugar in a stand mixer fitted with the paddle attachment and beat until light and fluffy. Turn the mixer off and scrape down the sides of the bowl.
One at a time, beat in the eggs, then slowly add the vanilla, milk and sour cream. Scrape down the sides of the mixer bowl as needed. With the mixer on medium speed, gradually add the flour mixture.
Line a muffin tin with paper muffin cups. Fill the muffin cups about two-thirds of the way with batter.
Bake for about 20 minutes, rotating the muffin tin halfway through and checking to make sure everything is going along great.
The cupcakes are done when a toothpick inserted into the middle of a cake comes out clean. Remove from the oven and let cool completely on a wire rack, then frost with Cream Cheese Frosting and decorate with candy or sprinkles.
Cream Cheese Frosting:
Beat together the cream cheese, butter, powdered sugar, vanilla and lemon juice in a stand mixer or with a hand mixer until light and fluffy.