Preheat your oven to 350
Over a double boiler with simmering water melt the chocolate and stick of butter in a large bowl. Once the chocolate and butter are completely melted and combined remove the bowl. Wipe the bottom of the bowl to ensure all condensation is removed. You don't want ANY water to accidentally drop into your bowl or the chocolate will seize.
In the same bowl slowly whisk in the brown sugar until the sugar is dissolved. The addition of the sugar will cool down the chocolate enough where you won't have to worry about your eggs scrambling.
Once the sugar is dissolved whisk in your eggs, one at a time, until they are full incorporated into the batter.
Now whisk in the coca powder, cayenne pepper, vanilla, and salt until everything is well combined.
Switch to a spatula and gently fold in the flour until it's fully incorporated into the batter.
Line a 8x8 baking dish with parchment paper. I sprayed the bottom of my pan with cooking spray so the parchment would stick to the pan, and not the brownies.
Pour the batter into the baking dish and smooth the batter out using your spatula. Then pop the baking dish in the oven.
Cook for 35-45 minutes.
Take the brownies out of the oven and let them cool, in the pan, until they are completely cool.
Finally, remove the brownies from the pan and gently peel off the parchment. Cut the brownies into 9 squares and enjoy!