In the bowl of a stand mixer, beat together the butter and sugars. Once it's creamy and smooth (about 10 minutes), mix in the eggs, orange juice, orange zest, and vanilla.
Sift together the flour, cinnamon, baking soda, cream of tartar, and salt. Mix thoroughly into the dough.
Fold in the chopped dark chocolate.
Refrigerate the dough for at least an hour.
Preheat the oven to 350ºF.
Scoop out 2 Tbsp-sized balls. Roll the balls between your palms until you have nice, smooth spheres.
In a bowl, mix together more orange zest, cinnamon, and sugar for your coating. My secret with the coating is to put the zest, cinnamon and sugar in a Nutribullet blender and pulse for 30 seconds. It gets extra fine and coats everything better.
Roll each ball in the coating mixture.
Place on a lined baking sheet 2-inches apart. Bake them for 12 minutes. Cool for 5 minutes on the sheet. Move to a cooling rack and allow them to cool completely.