Preheat your oven to 400°F and line a large baking sheet with parchment paper
Place the thinly sliced onions in a bowl and toss with olive oil until evenly coated
In a separate bowl, mix together the breadcrumbs, shredded cheddar, Parmesan cheese, garlic powder, oregano, salt, and pepper
Add the oiled onion slices to the cheese mixture and toss gently, pressing lightly so the coating sticks well
Spread the coated onions in a single layer on the prepared baking sheet to ensure they crisp evenly
Bake for 15–20 minutes, flipping halfway through, until golden brown and crisp around the edges
Remove from the oven and serve warm
In a small bowl, combine the ranch dressing and hot sauce and stir until smooth
Add cayenne pepper if you'd like a bit more heat
Stir in lemon juice and a pinch of black pepper for extra tang, if desired
Taste and adjust the heat by adding a little more hot sauce if needed
Refrigerate for at least 15–20 minutes before serving to let the flavors blend