Mix flour, cream of tartar, baking soda and salt.
Cream butter, adding 1 1/2 c. sugar gradually.
Add beaten eggs to butter/sugar mixture. Mix well.
Gradually add dry ingredients.
Chill dough at least 1 hour.
Shape chilled dough into balls (approx. 1 inch)
Roll in cinnamon/sugar mixture and place in well-greased miniature muffin tins.
Bake at 350 degrees 10 minutes or until set in center.
Immediately press one peanut butter cup into each cookie; cool slightly in muffin tins before removing to wire rack.
When peanut butter cups are partially set but still gooey, top each with a red or green m&m (I used Gingerbread m&m's but any kind would work!)