Preheat oven to 350°F
In a medium sized bowl sift together flour, confectioners sugar, cornstarch, and cream of tartar. Stir to combine and set aside.
In the bowl of a stand mixer with the paddle attachment attached add the butter. On medium speed, beat the butter until it has begun to go fluffy and creamy.
Scrape down sides of bowl and add in vanilla extract. Beat for 30 seconds until incorporated.
Add half of the dry mixture into the butter mixture. Mix until a sticky dough forms. Scrape down sides of bowl and add in the remaining dry mixture. Beat on medium speed until a thick dough forms. The dough may be a little crumbly, but to test it, pinch a bit of it between two fingers, if it sticks together it is ready to go!
Gather up the dough and form it into a ball. Let rest and chill in the refrigerator for 15 minutes.
Lightly dust a large surface with flour and roll out the dough to ½”-¼” thickness.
Using a round cookie cutter (or any cookie cutter of choice) cut out the cookies.
Place the cookies on a baking sheet, leaving at least 1” spacing between them. Top with sprinkles or turbinado sugar (optional)
Bake for 12 minutes, just until edges start to turn golden brown.
Remove from the oven and let the cookies sit on the baking tray for one extra minute. Transfer cookies to a wire cooling rack.