Preheat your oven to 350°F (175°C) to ensure even baking and perfect golden-brown cookies.
In a large mixing bowl, use an electric mixer to cream together the softened unsalted butter and 3/4 cup granulated sugar until light and fluffy, about 2-3 minutes.
Beat in the large egg and vanilla extract until fully incorporated.
In a separate bowl, whisk together baking soda, cream of tartar, salt, cocoa powder, and flour. Gradually add the dry mixture to the butter mixture, mixing until just combined.
Gently fold in the 2 teaspoons of instant espresso, distributing it evenly throughout the dough.
In a small bowl, mix 1/2 cup granulated sugar and 2 teaspoons cinnamon to create the cinnamon sugar coating.
Portion the dough using a cookie scoop or hands into 1-inch diameter balls. Roll each ball in the cinnamon sugar mixture until well coated.
Place the coated dough balls on a lined baking sheet about 2 inches apart. Bake for 10-12 minutes until edges are set but centers remain soft.
Remove from oven and let cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely. Enjoy!