Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
Peel the onions and slice them into very thin rings using a knife or a mandoline for uniformity.
In a mixing bowl, combine the shredded cheddar cheese, breadcrumbs, garlic powder, paprika, salt, and pepper. Mix well to combine.
Dip each onion ring into the olive oil, ensuring they are well-coated.
Then, dredge the onion rings in the cheese and breadcrumb mixture, pressing lightly to ensure the mixture sticks to the onion.
Arrange the coated onion rings on the prepared baking sheet in a single layer, ensuring they do not overlap.
Bake in the preheated oven for 15-20 minutes, or until golden brown and crispy.
Remove from the oven and let them cool slightly before serving. Garnish with fresh parsley if desired.
For extra flavor, consider adding herbs like thyme or oregano into the cheese and breadcrumb mixture.