Preheat oven to 400ºF.
Mix together the cinnamon and sugar in a small bowl and set aside.
Using an electric mixer beat together the sugar, shortening, butter, and eggs, until creamy.
In a separate bowl whisk together the flour, cream of tartar, baking soda, and salt.
Add the flour mixture to the butter, sugar and egg mixture and stir until well combined.
Using a 1-inch cookie scoop or Tablespoon form the dough into 1-inch balls. If your kitchen is warm and the dough is super soft, refrigerate the dough for about 45 minutes to an hour.
Roll each ball in the Cinnamon-Sugar Mixture. I like to make sure there is a good coating of cinnamon-sugar on the cookies, this gives them their amazing flavor!
Place on an ungreased cookie sheet about 2-inches apart. My favorite hack is to line the cookie sheet with parchment paper. You can re-use the same paper for multiple bakes and the clean up is a breeze!
Bake for 8-10 minutes. Cookies will puff up then flatten out. If you like crispy cookies, leave in the oven for a minute or two longer. For a softer cookie, remove from the oven when they just barely start to brown.
When just barely starting to brown, remove from oven and place the cookie sheet on cooling rack.
After cookies have cooled for about 10 minutes carefully remove from cookie sheet to cooling rack to finish cooling.
Then hide them or else they will be gone before you get a chance to try them!