In a mixing bowl, add flour, cornstarch, granulated sugar, baking powder, hot paprika, garlic powder, onion powder, ground sea salt and freshly ground black pepper.
Whisk to blend before pouring in beer. Whisk until the batter is nice and smooth; let it sit for 15 minutes.
Meanwhile, slice an onion to ½-inch thick and separate every layer into rings.
In a shallow dish, add about 1 1/3 cups course breadcrumbs and grind the remaining 2/3rds; stir and set aside.
15 minutes later, dip one ring at a time in the batter making sure it’s very well coated and hold it to let the excess batter drip off.
Transfer it to the breadcrumbs and toss it around so it’s well coated. Put it on a plate while working with the others.
In a heavy bottom skillet, heat up the oil until it reaches 375ºF/190ºC.
Working in batches, fry the onion rings for 1 to 2 minutes or until golden, flipping them halfway.
Transfer them on a plate or baking sheet lined with paper towels to absorb any excess oil while frying the others. Serve them immediately.