Combine onions, flour, salt, pepper and cayenne in a large Ziploc bag. Seal the bag and toss to coat onions with seasoned flour.

In a large pot, heat 2 inches of oil until it reaches 360 F. Shake excess flour off onions and fry in batches for 4 to 6 minutes or until golden brown and crispy. Remove with a slotted spoon and drain on paper towels. Continue with remaining onions until all are fried.

Serve immediately as a topping for burgers, hot dogs or grilled steak.