Preheat oven to 425 degrees F. Line two baking sheets with parchment paper. Lightly spray the parchment paper with olive oil cooking spray.
Stir together the buttermilk and cornstarch in a shallow bowl.
Stir together the flour, cornmeal, Parmesan cheese and House seasoning in a baking dish.
Coat the onion slices by placing each slice into the buttermilk mixture allow excess to drip before coating in the seasoned cornmeal. Then place the coated rings in a single layer on the baking sheets. Repeat until all onion rings are coated. Give the onion rings a light spray with non-stick baking spray. Bake until golden brown, about 20-25 minutes flipping once halfway through and serve hot.
Miss Brown’s House Seasoning:
Stir together the garlic powder, onion powder, paprika, salt and pepper in a small bowl.