Heat oven to 400 degrees.  

Cream together butter, shortening, 1 1/2 cups sugar, and eggs.

In separate bowl, mix together flour, cream of tartar, baking soda, and salt.

Slowly mix dry ingredients into butter mixture until thoroughly blended.

Shape dough by rounded teaspoonfuls into balls.

Mix together 3 tbsp sugar and 3 tsp cinnamon.  Roll dough balls in mixture.

Place cookies 2 inches apart on ungreased cookie sheet.

Bake 8 to 10 minutes, depending on preference for softness.  Remove immediately to rack to cool.  Store in an airtight container.