Preheat oven to 450 degrees.

Spray a baking sheet lightly with oil and set aside.

Place potato chips in the bowl of a food processor and process into crumbs, about 20 seconds. Transfer to a shallow bowl, add cayenne and set aside.

In another bowl, combine buttermilk, 2 T. flour, salt and pepper; set aside.

Slice onions into 1/2-inch slices and separate into rings, keeping only large, whole rings (reserve rest of onion for other uses). You should have about 12 to 14 rings.

Place the remaining flour in a resealable plastic bag, then add onions and shake to coat.

Dip onions one at a time into the buttermilk mixture, then dip into potato chip crumbs and place on baking sheet.

Spray with cooking spray evenly over rings and bake for 20 minutes or until coating is crisp. Serve immediately.