Preheat the oven to 350F. Coat an 8-inch square baking pan with flour-based cooking spray (recommend Baker's Joy). Alternatively, line the pan with foil that overhangs two sides and grease the foil.
On the stovetop, melt the butter in a small saucepan on medium heat. Set aside to cool until barely warm but still liquid.
In a large mixing bowl, sift together cocoa powder, dark cocoa powder, flour, espresso powder, ground sumac, and salt.
In a large glass measure with a pour spout, whisk together eggs, granulated sugar and brown sugar. Stir half of the egg mixture into the cocoa powder mixture. Stir in the melted butter. Finally, stir in the remaining egg mixture until just smooth. Do not over-mix.
Pour the batter into prepared baking pan, and level evenly in the pan using an offset spatula. Sprinkle Maldon salt over the top of the batter before baking. Don’t be shy here, Maldon salt is very thin and less salty than table salt. Sprinkle liberally to make sure the top is well-speckled with the salt.
Bake brownies about 20 minutes, or just until center is set (check at 20 minutes; bake for 5 more minutes if needed). Remove from oven and let cool in the pan. Turn out onto a wire rack to cool completely.
For neatest slices, refrigerate for 30 minutes before cutting, if desired. Brownies will stay fresh up to five days if stored in an airtight container, or frozen for up to two months well wrapped and double bagged in freezer bags.
Adapted from Ovenly: Sweet and Salty Recipes
Keyword brownies, dark chocolate brownies, ground sumac