Preheat the oven to 350 F. In a medium bowl, whisk together flour, cocoa powder, salt, baking soda, and cream of tartar. In a large bowl, combine butter with granulated and brown sugar until fluffy.
Add in egg and vanilla extract, and mix until smooth. Add in the flour mixture, and mix until it is fully combined. Add in the red food coloring and mix until it is fully red.
In a shallow dish, combine granulated sugar and cinnamon. Roll the cookie dough into balls, and roll into the cinnamon sugar mixture. Place the cookies onto a large ungreased baking sheet. Bake for 10-12 minutes.
