1. Preheat the oven to 375ºF / 190ºC.
2. Lightly butter cookie sheets or line them with parchment paper.

For the cinnamon coating:

1. In a small shallow bowl, mix the sugar and 1 1/2 teaspoons cinnamon. Reserve.

For the cookie dough:

1. Beat butter with sugar in a large bowl for 2 minutes, until creamy.
2. Add eggs, one at a time, and mix well.
3. Add vanilla and mix.
4. Sift dry ingredients: flour, cinnamon, baking soda, cream of tartar, and salt (I measure them and sift directly over the butter, but you can do it in another bowl if you want). Add to the butter and mix well until no dry spots remain. Don't overmix at this point.
5. Take teaspoons of dough and make balls the size of walnuts. 
6. Roll them in the cinnamon sugar and place them on the prepared baking sheet, spacing them a few inches apart as they expand during baking. 
7. Bake for 12-15 minutes, until the top is dry and the cookies barely start to crackle. 
8. Let cool for 5 minutes and lift them carefully with a spatula. Let cool completely on a wire rack and keep in tins or airtight cookie jars. 
9. You can chill the dough, covered to prevent dryness, for a day before baking.