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 ground cinnamon. Add in the eggs, melted butter, and vanilla extract until smooth.
Evenly divide the brownie batter between the paper liners. Bake for 15-20 minutes.