Melt the butter in a small saucepan over medium-low heat. Let it bubble and boil while mixing often and watching carefully, until it begins to brown (it burns very easily). Once the milk solids are a toast-y brown color, remove from the heat and pour into a glass or metal bowl. Add the salt, espresso powder, and cayenne pepper and whisk until combined. Let the mixture cool at room temperature for 10 minutes.
Line an 8x8 inch or 9x9 inch square baking pan with parchment paper (I used a 9x9 inch pan FYI). Preheat the oven to 350 degrees F (177 C).
After 10 minutes, add the chocolate and let it sit undisturbed for a few minutes. Once 3-4 minutes has passed, whisk until the chocolate is completely melted and smooth.
Using a stand mixer or a large mixing bowl and an electric hand mixer, whip the eggs and brown sugar on high for about 2 minutes or until fluffy and lightened in color. Add the butter/chocolate mixture and fold to combine using a spatula. Sift in the baking powder, Dutch cocoa, and GF flour and carefully fold the mixture to fully incorporate the wet and dry ingredients. Pour the batter into the prepared baking pan and bake for 20-25 minutes or until a toothpick comes out dirty but not so much that the batter is dripping off (it should be messy but not runny, took mine 23 minutes). Remove from the oven and let it cool for at least 15 minutes before digging in and enjoying. Hope you like these tricky brownies! Happy spooky season!!
