Preheat your oven to 350°F (175°C) and grease an 8×8-inch baking dish.

In a medium bowl, whisk together cocoa powder, flour, sugar, cinnamon, nutmeg, and salt until well combined.

Melt the butter in a small saucepan over low heat or in the microwave, then let cool slightly. Stir in eggs and vanilla extract.

Pour the wet mixture into the dry ingredients and stir until just combined; avoid overmixing.

Spread the batter evenly in the prepared dish and bake for 25-30 minutes or until a toothpick inserted comes out with moist crumbs.

Allow to cool completely before slicing into squares.