Tennessee Onions

3 to 4 sweet onions, we used Vidalia
4 T butter
1 tsp salt, or to taste
1 tsp garlic powder
1/2 tsp oregano
1 C shredded Italian blend cheese
1 C shredded cheddar cheese
1/2 C shredded parmesan cheese

Heat oven to 350 degrees and prepare a 9x13-inch dish with non-stick cooking spray. Turning the onion sideways, slice into 1/4-inch rounds and separate the rings. Spread onion rings in baking dish and sprinkle with the salt, garlic powder, and oregano. Slice the butter into approximately eight pats and place evenly across dish. Sprinkle the Italian blend and cheddar cheese over the onions and then add the parmesan on the very top. Bake for 35 to 40 minutes or until cheese is starting to bubble and brown. Serve while still hot.