In a small bowl, mix together the 2 tbsp sugar and the cinnamon. Set aside.
In a medium bowl, sift together the flour, cocoa powder, baking powder, salt, and cayenne pepper, if using. Set this aside.
In a large bowl with a handheld mixer, or in the bowl of a stand mixer, beat the butter and sugar on medium speed for 3 to 5 minutes, until pale and fluffy. Scrape down the sides of the bowl.
On low speed, beat in the eggs and vanilla until well incorporated. Carefully add the flour mixture, pulsing on and off to avoid a cloud of chocolate flour, until just combined.
Cover the bowl with plastic wrap and refrigerate for 2 hours.
Preheat oven to 350° F.
Shape the dough into one-inch rounds and roll them in the cinnamon sugar mixture. Place on baking sheets lined with parchment paper, spacing about 2 inches apart.
Bake the cookies until the edges are set and the cookies are puffed, about 10-12 minutes. If desired, sprinkle with a little additional cinnamon sugar immediately upon removing from the oven.
Cool the cookies on the baking sheets for about 5 minutes before transferring to a wire rack to cool completely.
The cookies will keep in an airtight container at room temperature for up to 3 days.
*To freeze unbaked cookie dough, roll into balls and place on lined baking sheet. Freeze until solid and then place cookie dough balls in ziptop bag. To bake from frozen, remove from freezer, roll in cinnamon sugar mixture, and place on baking sheet. Bake for an additional 3-5 minutes.