Slice the ⅓ cup butter into pieces and melt it in a light-colored skillet over medium heat stirring or whisking constantly. Once melted, the butter will begin to foam. Continue stirring/whisking for about 5-7 minutes, the butter will become a deep amber color. Remove the browned butter from the heat, and pour it into a bowl. Allow the butter to cool for 30 minutes.
Line a 9 x 9-inch baking pan with parchment paper allowing the ends to extend over two of the sides. Grease the pan with cooking spray. Preheat the oven to 350°F (180°C) and position an oven rack in the middle of the oven.
In a large bowl, mix the butter, 1 cup Nutella, ¼ cup brown sugar, ¼ cup granulated white sugar, 2 large eggs, 1 egg yolk, and 2 tablespoon hazelnut liquor until combined.
Add the ½ cup all-purpose flour and ½ teaspoon kosher salt and stir until just combined.
Pour the batter into the prepared baking dish.
Pour the ½ cup raspberry jam over the brownie batter.
Heat the ½ cup Nutella in the microwave for 30 seconds to soften. Drizzle the Nutella over the raspberry jam and use a knife to swirl the two together.
(Optional) Dot the surface of the brownies with fresh raspberries.
Bake for 45-50 minutes or until a toothpick inserted in the center comes out with very moist crumbs clinging to it. Remember the brownies will continue to bake as they cool.
Cool completely before using the parchment paper to lift the brownies from the pan and cut them into squares.