Preparation

1. Preheat your oven to 350°F (175°C).
2. Coat a 9×13-inch baking dish with non-stick cooking spray.
3. Clean and peel the Vidalia sweet onions, then slice them into ¼-inch thick rounds. Do not separate the rounds into individual onion rings.
4. Evenly spread the onion rounds across the base of the prepared baking dish.
5. Season the onion rounds with salt, garlic powder, and oregano.
6. Cut the butter into eight equal portions and distribute them evenly over the seasoned onions.
7. Evenly sprinkle the Italian blend cheese and cheddar cheese over the onion rounds, followed by a final layer of shredded Parmesan cheese.
8. Place the baking dish in the preheated oven and bake for 35-40 minutes, or until the cheese is browned and bubbling.
9. For the best taste, serve the dish warm.