Prepare the ingredients for making Nutella Blondies.
Melt butter in a saucepan over medium heat, then cook until the solids turn brown.
Add the sugars to the butter and stir well until smooth.
Allow the mixture to cool before adding the eggs, vanilla and salt.
Stir through the flour and then the nuts.
Combined until you don't see any streaks of flour. Don't overmix.
Transfer the mixture to a lined pan and level it out.
Load the Nutella into a piping bag or a zip-top bag with a corner cut off.
Squeeze it in thick ribbons over the batter
Use a skewer to marble the Nutella and batter together.
Bake the Nutella blondies until edges brown but center looks slightly underdone, about 15 minutes.