Heat the vegetable oil in a deep fryer or large pot to 350°F (175°C). Ensure sufficient oil to fully submerge the onion rings, about 2-3 inches deep.

In a medium bowl, combine the all-purpose flour, garlic powder, paprika, salt, and black pepper. Whisk together until evenly mixed.

Prepare three bowls: one with buttermilk, another with the flour mixture, and the last with panko breadcrumbs.

Dip each onion ring into the buttermilk, then coat in the flour mixture, shaking off any loose flour.

Return the onion ring to the buttermilk briefly, then dredge into the panko breadcrumbs, pressing gently to adhere.

Carefully lower coated onion rings into the hot oil, frying for about 2-3 minutes until golden brown and crispy.

Remove fried onion rings with a slotted spoon, letting excess oil drip off, and transfer to a plate lined with paper towels.

Serve warm with a variety of dipping sauces like ranch or zesty aioli.