Preheat your oven to 400℉ Line a 12x17 inch metal sheet pan with parchment paper. Sprinkle the parmesan cheese on the pan to form an even layer, covering the bottom of the pan. Place the brussels sprouts cut side down, close to each other but not touching. Lightly brush each one with olive oil and sprinkle a little salt, pepper and onion powder on them. Bake for 15-18 minutes or until the cheese turns golden brown in the middle. Allow to cool for a few minutes and then tear/brake apart with your hands. Enjoy!