Soak onion rings in a bowl of ice water for 1 hour; drain.

Combine flour and seasonings in a large plastic bag; pour buttermilk into a shallow dish. Dip onion rings in the buttermilk, then transfer a few at a time to the flour using a skewer for easy maneuvering. Dip rings a second time into the buttermilk and flour using the skewers. Set the coated, skewered rings over a bowl while coating the remaining onions.

Heat 3" oil in a pot over medium-high to 365°. Fry half the onions in the oil until golden, 3–4 minutes. Remove from the oil using skewers, then rest over a bowl to drain. Fry remaining onions in the same way.

	For scallions, first remove root end. Trim ragged green end and rinse thoroughly. Cut diagonally using both white and green parts.