Spray a 9x13" baking dish with cooking spray.
Cut the loaf of bread into 1" chunks and evenly spread them in baking dish.
In a large bowl, whisk together the eggs, milk, sugar, cinnamon, and vanilla extract.
Pour the egg mixture over the bread chunks, making sure it gets evenly distributed. You may need to press some of the top pieces down into the liquid just a little.
Place Nutella in a microwave-safe bowl and microwave for 30-60 seconds, until it is drizzle-able.
Drizzle the warm Nutella over all of the casserole, making sure it is evenly distributed and in all of the little nooks and crannies.
Cover with foil or plastic wrap and refrigerate overnight.
Once ready to bake, preheat the oven to 350 degrees F.
Bake uncovered for 45-55 minutes, until golden brown and egg mixture has set.
Serve topped with additional warm Nutella, powdered sugar, and raspberries.