Preheat oven to 350 degrees. Butter an 8-by-11-inch baking pan. Line with parchment paper. Butter parchment.Advertisement
Whisk flour, baking powder, and salt.
Melt butter. Beat butter and sugar until combined. Beat in eggs and vanilla. Add flour mixture, and stir until combined. Stir in hazelnuts and Nutella.
Press dough into pan. Bake until a toothpick comes out with a few moist crumbs, about 25 minutes. Let cool 15 minutes. Cut into squares. Serve with additional Nutella.
Blondies can be stored in an airtight container up to 2 days.