In a high-sided saucepan, heat the oil over medium heat until it reaches 350 degrees F.
Mix together the cayenne, paprika, garlic powder, basil, oregano, black pepper and sea salt in a small bowl.
Whisk together the flour and cornmeal in a medium bowl. Toss the onion rings in the flour mixture to coat. Deep-fry the onion rings in 2 batches until crispy and lightly golden, 3 to 5 minutes. Drain on a paper towel for 1 minute, and then transfer to a large bowl. Add a large pinch of the spice mixture, and toss the onion rings to evenly distribute the seasoning.
Season with more salt if desired, and serve immediately.