Preheat oven to 350*.
Cream butter, shortening, and sugars together until fluffy.
Add Vanilla, Egg, Cream of Tartar, Baking Soda, and Salt. Mix well.
Add Flour and mix to combine.
Using a small teaspoon cookie scoop, set scoops 3" apart. Lightly smoosh with a fork or a glass.
Bake 350* for 10-12 minutes or until edges look set and cookies are golden.