Preheat oven to 375º F.
Spread onion rings out in a 9×13-inch baking dish, keeping rings and layers intact, then drizzle with olive oil and season generously with salt and pepper.
Place baking dish in oven and roast for 15 minutes, or until softened.
Remove onions from oven and raise temperature to 450º F.
Combine heavy cream, wine, butter, garlic powder and cayenne in a medium saucepan over medium heat and cook until butter is melted and bubbles form on the outside edge of cream.
Remove mixture from heat, then pour over pre-roasted onions, sprinkling parmesan cheese over all the onions.
Top baking dish with aluminum foil and bake for another 20 minutes. Remove foil and cook for another 5-10 minutes, or until onions are caramelized and cheese is golden brown.
Remove dish from oven and serve hot. Enjoy!