01 -
Preheat oven to 350 degrees Fahrenheit. Line baking sheets with parchment paper or silicone mats.
02 -
In the bowl of a stand mixer with the paddle attachment, cream the butter and sugars. Add eggs and vanilla. Scrape bowl. Mix well.
03 -
In a separate large bowl, whisk together the flour, cocoa powder, cream of tartar, baking soda, baking powder, and salt.
04 -
Add dry ingredients to the wet ingredients while mixing on low speed. Mix until just incorporated.
05 -
Scoop dough and round into balls (about 2 Tbsp each). Mix together the sugar and cinnamon in a bowl. Roll cookie dough balls in cinnamon-sugar.
06 -
For softer and thicker cookies, chill dough on tray in the freezer for 10 minutes or refrigerator for 30+ minutes before baking.
07 -
Bake at 350˚F for 9-11 minutes, or until edges are set and the middle is still soft and slightly shiny.
08 -
Immediately sprinkle extra cinnamon-sugar on top of the baked cookies while still hot. Let rest on tray for 2 minutes before transferring to a rack.