Preheat oven to 350 degrees and line 2 cookie sheets with parchment paper
Using a large bowl, beat together the butter, brown sugar, and sugar until combined and creamy
Beat in the eggs, 1 at a time until combined
Beat in the vanilla
Using another large bowl, whisk together the flour, cocoa powder, cream of tartar, baking soda, baking powder, and salt until combined
Gradually mix in the dry ingredients into the wet ingredients until combined and a dough forms
Using a small bowl, whisk together the 1 C of sugar and 1 tsp of cinnamon
Using a small ice cream scooper, scoop out about 1 ½ tbsp of cookie dough
Roll into a ball in your hands
Coat cookie dough ball in the cinnamon-sugar mixture
Place onto a cookie tray
Place into the oven and bake for 10-12 minutes or until the edges are set and the middle looks soft
Allow cooling completely before enjoying