Preheat the oven to 350. Line a 9x9-inch baking pan with parchment paper.
Whisk sugar, flour, and salt in medium bowl.
Add butter. Mix until mixture forms into dough.
Press dough evenly into prepared baking pan. Bake for 15 minutes or until edges are just golden brown. Set on cooling rack.
Nutella Cheesecake Filling
Blend cream cheese, vanilla extract, sugar, egg, and 1 Tbsp. Nutella at medium speed until the mixture is uniform. Set aside.
Warm 3 Tbsp. Nutella in the microwave for one minute at 50% power. Stop to stir the mixture every 15 seconds. Set aside.
Pour cream cheese filling on top of baked shortbread cookie base. Use spatula to create an even layer.
Drizzle vertical lines of the warmed Nutella on top of the cream cheese layer with a spoon. To create swirls, dip a knife or chopstick half way into the filling and make small circles.
Bake for 15 minutes or until filling is set. Place on cooling rack for 30 minutes, then transfer to refrigerator for another 30.
Cut Nutella Cheesecake into 32 cheescake bars and store in the refrigerator.