Preheat oven to 350 F and line baking sheets with parchment paper.
In large bowl or stand mixer beat the butter and sugar until fluffy. I like to mix mine for a solid 3 minutes.
Add in the egg and vanilla extract and continue mixing till ingredients are well combined.
In a separate bowl whisk together flour, baking powder, baking soda, cream of tartar, and salt.
Add the dry ingredients to the wet and mix until everything is combined.
Add in the sprinkles and mix once more.
Scoop dough into a 1.5 tablespoon balls and make them round. Dip the top and sides of the balls in some extra sprinkles. Arrange on the lined baking sheet 2 inches apart.
Bake for 8 minutes or until the bottoms are golden brown. The cookies may seems a little underdone but will stiffen up after they've cooled.
Allow cookies to cool on the pan for 5 minutes before moving them.