Preheat oven to 425˚F (220˚C). Line large baking sheet with parchment paper. Cut onion into 1/2-in. (1-cm) thick rounds; separate into rings. Soak 12 of the largest rings in buttermilk for 10 min., until the onion begins to soften. Reserve remaining onion for another use.
In bowl, toss breadcrumbs with cheese and garlic powder; set aside. In second bowl, place the flour. In third bowl, fork-beat the egg. One onion ring at a time, coat each in flour, then beaten egg, then roll in breadcrumb mixture until well coated. Place rings on the parchment. Drizzle with olive oil.
Bake 12 to 15 min. until onion rings are golden brown.
To prepare a buttermilk substitution, whisk 1/4 tsp (1 mL) white vinegar into 2/3 cup (150 mL) milk.
Avoid using cooking onions for this recipe. Vidalia, Spanish or any sweet onion makes for tasty and tender onion rings.
Sauté remaining onion in olive oil and use as a topping for burgers, sausages or pizzas.