In a large bowl, or the bowl of a mixer, cream together butter and sugar until it is smooth and well combined. Add the egg, egg yolk and vanilla to the bowl and continue to mix it until well blended. Then, mix in the cream of tartar, baking soda, and salt.
Pour in the flour about 1 cup at a time, mixing until just blended before adding the rest. Once the flour is fully incorporated, stop mixing.
Mix together the cinnamon and sugar in a small bowl.
Individually, scoop about 1 ½ tablespoon size dough balls and roll them between your palms until slightly smooth. Place the dough balls into the bowl of cinnamon sugar and rotate them while using your other hand to sprinkle more cinnamon sugar over the top. Once completely coated, place the dough balls onto your prepared baking sheet and press down lightly with your palm to flatten the balls just slightly.
Bake in a pre-heated oven for 9-11 minutes. Cookies will still be soft upon removal from the oven.