In a large mixing bowl, cream the softened butter with both granulated and brown sugars until the mixture becomes pale and fluffy. Beat in the eggs one at a time, then add the vanilla extract, mixing until smooth and fully incorporated.
In a separate bowl, whisk together the flour, cocoa powder, ground cinnamon, chile powder, cayenne pepper (if using), baking soda, cream of tartar, and salt. Gradually add the dry mixture into the butter and sugar mixture, mixing just until the dough comes together and no streaks remain.
Cover the dough and place it in the refrigerator to chill for at least 30 minutes, allowing the flavors to deepen and the dough to firm up for easier shaping. While the dough chills, preheat the oven to 350°F (175°C) and line baking sheets with parchment paper.
In a small bowl, combine the rolling sugar and cinnamon. Scoop out dough and shape it into balls using about 1 to 1½ tablespoons of dough per cookie. Roll each ball thoroughly in the cinnamon-sugar mixture and space them generously apart on the prepared baking sheets to accommodate spreading.
Bake for 10 to 12 minutes, or until the edges are set and the centers are slightly soft. Immediately transfer the cookies to a wire rack to cool, where they’ll continue to firm up slightly and develop their chewy texture. Keep the remaining dough chilled between batches.