Preheat oven to 400℉.
Place silpat liners or parchment paper on cookie sheets. Set aside.
Place sugar and softened butter in the bowl of a stand mixer.
Blend on high speed until creamed together and mixture is light and fluffy, about 3 to 4 minutes. Scrape down the sides of the bowl as needed.
Reduce speed to low and add eggs one at a time, then add vanilla. Mix until well combined.
Slowly add the dry ingredients; flour (a cup at a time), the Cream of Tartar, baking soda, and salt.
Increase speed to medium and mix until fully incorporated, scraping down the sides of the bowl as needed.
Use a cookie scoop to form 1½ inch balls of dough.
Roll dough balls in the reserved cinnamon sugar mixture to coat the balls of dough completely.
Place dough balls on a cookie sheet 2 inches apart.
Bake for 10-12 minutes until the edges just start to brown. Centers should still look doughy, don't over cook them.
Remove from oven and allow cookies to cool for 2-3 minutes on the cookie sheet.
Using a spatula, transfer cookies to a cooling rack and allow them to cool completely.
Once completely cooled, store cookies in a covered container for up to 2-3 days.