01 -
Preheat your oven to 175°C (350°F).
02 -
Coat a 9×13-inch baking dish with non-stick cooking spray.
03 -
Clean and peel the Vidalia sweet onions. Slice them into rounds approximately ¼ inch thick, ensuring that the rounds remain intact.
04 -
Spread the onion rounds evenly across the base of the prepared baking dish.
05 -
Season the onion rounds with salt, garlic powder, and oregano.
06 -
Cut the butter into eight even portions and distribute them evenly across the seasoned onion rounds.
07 -
Sprinkle the Italian blend cheese and cheddar cheese evenly over the onion rounds. Add a final topping of shredded Parmesan cheese.
08 -
Place the baking dish into the preheated oven and bake for 35-40 minutes until the cheese is browned and bubbling.
09 -
Serve the dish promptly while it remains warm.