Separate the onion slices into rings and set them aside.

In one shallow dish, whisk together the buttermilk and egg until smooth.

In a second shallow dish, combine the flour, cornstarch, salt, pepper, garlic powder, and smoked paprika. Mix until evenly distributed.

Pour the panko breadcrumbs into a third shallow dish.

Dredge each onion ring in the flour mixture, ensuring it’s fully coated. Then dip it into the buttermilk mixture, letting any excess drip off. Finally, press it into the panko breadcrumbs, coating both sides completely. Set aside on a plate.

Heat 2 inches of vegetable oil in a heavy-duty pan or cast-iron skillet over medium heat. Use a thermometer to maintain the oil at 350°F (175°C).

Fry the onion rings in batches, being careful not to overcrowd the pan. Cook each batch for 2-3 minutes, flipping halfway through, until golden and crispy.

Transfer the cooked onion rings to a plate lined with paper towels to drain excess oil. Sprinkle with a little salt while still hot. Serve immediately with your favorite dipping sauces. Enjoy!