For the cookies:
flour
baking powder
baking soda
salt
butter
sugar
eggs
vanilla extract
Rainbow sprinkles
Frosting:
Unsalted butter
Powdered sugar
Vanilla extract
Salt
Bake in the preheated oven for 7-9 minutes, until cookies have spread and are slightly golden. Allow the cookies to cool for 5 minutes on the pan before transferring to a rack to cool completely.
To prepare the frosting, beat the butter until smooth. Then add the powdered sugar gradually and continue mixing until smooth. Lastly, mix in the vanilla and salt. Pipe the frosting on the cooled cookies. Sprinkle the frosted cookies with sprinkles.