Prep the pan – Preheat oven to 350°F. Grease an 8x8-inch baking pan and line with parchment paper.
Make the batter – In a large bowl, whisk together Nutella and eggs until fully incorporated and no streaks remain, about 1 minute of vigorous stirring. Stir in flour and salt until combined. Batter will be very thick.
Bake – Pour batter into the prepared pan and spread evenly. Bake at 350°F for 20–25 minutes or until edges look set.
Cool completely – Allow brownies to cool completely in the pan before slicing. They will look underdone when pulled from the oven but will continue to set as they cool.
Notes
For extra fudgy brownies, pull them when the toothpick still has a few moist crumbs — they'll firm up perfectly as they cool. Use room temperature eggs for easier mixing, and be sure to spoon and level your Nutella when measuring.