Preheat oven to 400°F.
Thinly slice the onion and separate the rings.
In a shallow bowl, combine the flour, paprika, garlic powder, cayenne, salt, and black pepper.
Dredge the onion rings in the flour mixture, shaking off any excess.
Arrange the coated onion rings on a baking sheet.
Bake for 15-20 minutes, flipping halfway, until golden brown and crispy.
In a medium bowl, mix together the mayonnaise, sour cream, ketchup, horseradish, Worcestershire sauce, and lemon juice.
Serve the baked onion rings with the dipping sauce.
