Preheat oven to 350 degrees F and line two cookie sheets with parchment paper.
Whisk together the flour, cocoa powder, cream of tartar, baking soda, cinnamon, salt, espresso powder, and cayenne (if using) in a medium bowl.
2 cups all purpose flour, ⅔ cup cocoa powder, Dutch process, 2 teaspoons cream of tartar, 1 teaspoon baking soda, ¾ teaspoon cinnamon, ½ teaspoon fine sea salt, ½ teaspoon instant espresso powder, ½ teaspoon cayenne pepper
In the bowl of a stand mixer, combine the butter, brown sugar and granulated sugar. Beat on medium speed and cream the mixture for 2-3 minutes until light and fluffy.
1 cup unsalted butter, room temperature, 1 cup light brown sugar, packed, ½ cup granulated sugar
Beat in the vanilla extract, and the eggs, one at a time, scraping the bottom and sides of the bowl after each addition.
2 large eggs, 1 teaspoon pure vanilla extract
On low speed, add the flour mixture, beating just until incorporated.
Scoop the dough with a medium size/2 tablespoon ice cream scoop onto a lined cookie sheet.
Roll the scooped dough into balls.
In a small bowl, whisk together the ¼ cup of granulated sugar and 1 teaspoon of cinnamon.
¼ cup granulated sugar, 1 teaspoon cinnamon
Roll the dough balls in the cinnamon sugar mixture to coat. Place on the prepared cookie sheets, leaving 2" between the cookies.
Bake the cookies for 10 minutes or until the tops look just set. Let the cookies cool on the baking sheet for 5 minutes before transferring to a cooling rack to cool completely.