Peel onions. Slice into 1/4 - 1/2-inch slices.

Place onion rings in large bowl.

Pour buttermilk over onions. Toss and press to make sure all onion rings are covered and submerged. Place bowl in refrigerator and allow rings to soak for 2 - 3 hours.

When ready to cook, place flour, salt, pepper and cayenne in a large bowl. Mix well.

Pour enough oil to deep fry rings into a large pot, Dutch oven or deep fryer.

Heat oil to 375°F.

Grab a small handful of onions from the buttermilk, allowing excess to drip off, and place into flour mixture. Toss to coat fully.

Place breaded rings into hot oil. Add another handful or two, if you have room, but do not crowd.

Fry for 2 - 3 minutes until golden brown. Remove to a paper towel-covered plate to drain.

Repeat until all onions are fried.

Serve immediately, hot.