Preheat & Prep: Preheat your oven to 350°F (175°C). Line an 8x8-inch square baking pan with parchment paper, leaving an overhang for easy lifting.
Melt Butter & Chocolate: In a small saucepan over low heat, melt the butter and chopped dark chocolate together, stirring until smooth. Remove from heat and let cool slightly.
(If using only cocoa powder, melt butter first, then whisk in cocoa.)
Whisk Wet Ingredients: In a large mixing bowl, whisk together the sugar, eggs, and vanilla for 1–2 minutes until pale and slightly thickened. This helps create the shiny brownie top.
Combine Mixtures: Slowly pour the melted chocolate mixture into the egg mixture, whisking constantly until glossy and smooth.
Add Dry Ingredients: Sift in the gluten-free flour, cocoa powder, and salt. Gently fold together with a spatula until just combined — do not overmix.
Add Mix-Ins: Fold in chocolate chips, nuts, or any other add-ins if using.
Bake: Pour the batter into the prepared pan, spreading evenly. Bake for 20–25 minutes, or until the center is set but still slightly soft. A toothpick should come out with moist crumbs, not clean.
Cool & Slice: Allow brownies to cool completely in the pan for at least 30 minutes. Lift out using parchment paper and slice into squares.