1. In a stand mixer, mix the butter on medium speed for about a minute until creamy. Add the sugar and mix again until fluffy, about 2 more minutes. Mix in egg and vanilla and mix on low until just combined. Scrape down the sides as needed. and set aside.

2. In a medium size bowl, whisk together the flour, salt, baking powder, baking soda, and cream of tartar. Add the dry ingredients to the wet ingredients a little at a time. Once combined, fold in 1/2 cup sprinkles by hand.

3. Scoop a large sections of dough (about 2 Tablespoons of dough each) and roll into balls and put onto a baking sheet prepared with a Silat mat of parchment paper. Press down the middle of the balls so they flatten out a bit. Add a few more sprinkles on top of each ball dough.

4. Chill the balls of dough on the cookie sheet for about an hour. This step will prevent spreading in the oven.

5. Preheat oven to 350 degrees. Bake for 11-12 minutes. The cookies will appear very soft in the centers. Allow the cookies to cool on the cookie sheets for 3 minutes and then move to wire rack to cool completely.