Whisk together the dry ingredients: flour, salt, baking soda, and cream of tartar. Set aside.
In a mixing bowl, beat the butter & 1 ½ cups sugar for several minutes until fluffy.
Add eggs, one at a time.
Add half the dry ingredients to butter mixture, mix until just combined, then repeat with the other half.
Let the dough chill in the fridge for an hour or so.
When the dough is cold, preheat the oven to 350°F. Mix together the cinnamon and remaining sugar in a shallow bowl.
Roll the dough into small balls, about 1 inch. Roll in the cinnamon sugar to coat fully, then put on a greased baking sheet. Make sure you position them pretty far apart, these expand a lot.
Bake 12-13 minutes, and pull when the edges are golden brown. Let rest on the cookie sheet for a minute, then put on a cooling rack for a few minutes.