Preheat and prepare the pan.
Preheat the oven to 350 degrees and spray a 8x8 baking pan with coPreoking spray. Set aside.
Make the batter.
In a medium bowl, combine 1 c Nutella, the eggs, and the flour. Use a spatula to thoroughly combine the ingredients, leaving no white streaks of flour visible. Pour into prepared pan. Spoon remaining Nutella on top of brownie batter and swirl with a butter knife.
Bake for 28-32 minutes or until a toothpick inserted in the center comes out clean. If brownies are browning too quickly tent with foil half way through the baking process. Remove from oven and cool completely before cutting.
Remove from pan and place on a cutting board. Cut 16 even squares and dust with powdered sugar (optional) before serving.
Adapted from The Comfort of Cooking