Preheat the oven to 350 F and line a 6-cup muffin pan with cupcake liners. Set aside.

In a small bowl, whisk together the flour, baking powder, and salt. Set aside.

In a medium bowl, beat the butter and sugar until light and fluffy.

Add the egg and vanilla, beating until combined.

Gradually add the flour mixture, beating on low speed. Add the milk and beat until combined.

Transfer the batter to the prepared muffin pan and bake for 15 minutes or until a toothpick inserted in the center of a cupcake comes out clean.

Let cool for 10 minutes in the pan before transferring to a wire rack to cool completely.

In a medium bowl, beat the butter until creamy.

Add the powdered sugar, beating on low speed until just combined.

Add the milk and vanilla extract. Beat on medium high speed until light and fluffy.

Divide the frosting into two bowls. In one bowl, stir in a couple drops of light pink gel food coloring. In the other bowl, stir in a couple drops of light blue gel food coloring.

Transfer the frostings to piping bags. Place a large star tip in a large piping bag. Then, cut the ends off of the piping bags filled with frosting and place them both into the larger piping bag with the large star tip.

Pipe a swirl of frosting onto the top of each cupcake. Apply even pressure to the bag so that the two frostings come out evenly and create the swirl effect.

Press a gold crown cupcake topper into the frosting on each cupcake.