Preheat your oven to 350°F (175°C). This step is crucial for ensuring your brownies bake perfectly.
Line your 9x9-inch baking pan with parchment paper, leaving some overhang on the sides. This will make it easy to lift the brownies out once they are baked.
In a microwave-safe bowl, melt the unsalted butter. Allow it to cool slightly before using it in the batter.
In a large mixing bowl, whisk together the melted butter and Nutella until smooth and well combined.
Crack in the four large eggs, adding them one at a time, and mix in the granulated sugar. Whisk until the mixture is smooth and glossy.
Add the gluten-free flour, cocoa powder, salt, and vanilla extract to the wet mixture. Use a spatula to fold the ingredients together until just combined. Be careful not to overmix.
Pour the brownie batter into your prepared baking pan, spreading it out evenly.
Place the pan in the preheated oven and bake for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (not wet batter).
Once baked, remove the brownies from the oven and let them cool in the pan for at least 10 minutes. Then, lift them out using the parchment paper, cut into squares, and enjoy!