Place slices of onion in a shallow dish.

Pour the buttermilk over the top and let them soak for about 1 - 2 hours, refrigerated.

Preheat oven to 450 degrees Fahrenheit.

Line baking sheet with parchment paper or foil.

Combine panko, bread crumbs, and corn flakes and place half of the mixture in a large dish; season with salt. Reserve the rest for after coating.

Dip each soaked onion ring into the crumb mixture; coat well.

Place rings onto two cookie sheets.

Lightly spray with olive oil spray.

Bake about 12 minutes or until golden brown.

Serve immediately.