Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a medium bowl, whisk together flour, cocoa powder, baking powder, and salt.

In a large mixing bowl, beat together granulated sugar, brown sugar, and eggs until light and fluffy, about 2-3 minutes, then stir in vanilla extract.

Gently fold the dry ingredients into the wet mixture until just combined.

Chill the dough in the refrigerator for at least 30 minutes.

Combine additional granulated sugar and ground cinnamon in a small bowl for the coating.

Scoop portions of dough and roll into balls, then coat in the cinnamon sugar mixture.

Place cookie balls on the baking sheet, spaced 2 inches apart, and bake for 10-12 minutes.

Let cookies cool on the baking sheet for 5 minutes before transferring to a wire rack.