In the bowl of an electric mixer, cream the butter until it is light and fluffy, or about 2 minutes. Add the sugar and mix again until light and fluffy. Slowly add the eggs, and mix until incorporated.
In a separate large bowl, mix together the flour, cream of tartar, baking soda, and salt. Add the dry ingredients to the butter mixture and mix on low until the cookie dough is well incorporated. Cover the bowl with plastic wrap and chill in the fridge for 20 minutes.
Remove the dough from the fridge and scoop into 1 1/4" balls. In a small bowl, combine the sugar and cinnamon, then roll your cookie dough balls into the cinnamon sugar. Place about 2" apart on a greased baking sheet.
Bake in your preheated oven for 8-10 minutes, or until golden brown on the edges.
Remove the cookies from the oven and let them cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely. Enjoy!
Notes
Storing instructions: store in an airtight container at room temperature for up to 3 days, or in the freezer for up to 2 months.