Preheat the oven to 350°F. Oil and line an 8 x 8 square baking pan.
Mix together the sugars, eggs, and vanilla in a large bowl until blended. Add the hazelnut flour, Nutella, and cocoa powder and mix until batter is smooth.
Pour the batter into baking pan and bake for about 25 minutes, until toothpick inserted comes out clean. Let cool completely before cutting.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.