Preheat the oven to 350 F. Line a 12 cup muffin pan with paper liners. In a large bowl, whisk together flour, sugar, cocoa powder, salt, baking soda, and cream of tartar.
Add in the eggs, melted butter, and vanilla extract, whisk until smooth. In a medium bowl, whisk together flour, salt, baking soda, and cream of tartar. In a large bowl, combine butter with sugar until fluffy.
Add in egg and vanilla extract, and mix until smooth. Add in the flour mixture until it is fully combined. In a small bowl, combine sugar and cinnamon.
Evenly divide the brownie batter between the paper liners. Evenly top with the cookie dough. Sprinkle with the cinnamon sugar mixture. Bake for 15-20 minutes.
