Preheat oven to 375. Cream butter, 1 1/2 cups sugar until fluffy.
Add eggs and vanilla. Beat until smooth.
In a medium bowl combine flour, cocoa, 1 tsp cinnamon, cream of
tartar, baking soda and salt.
In a small bowl combine remaining 3 tblsp sugar and 1 3/4 tsps
cinnamon. Shape dough into 1" balls and roll in sugar mixture.
Place 2" apart on lightly greased sheet. Bake 6 to 8 minutes until
lightly browned. Transfer to wire rack to cool.