Sift together flour, cream of tartar, baking soda and salt.
Cream butter, vanilla and sugar until light and fluffy. Add eggs and beat well. Add sifted dry ingredients, a fourth at a time, stirring to mix thoroughly. Chill 1 hour.
Shape dough in 1" balls and place 2½" apart on greased baking sheet. Flatten by pressing with bottom of drinking glass coated