Green onions have a tendency to become viscous—a trait that vinegar modifies. Lively and fresh, this quick pickle serves as relish and salsa—a bright note on an antipasto tray or tart vegetable side to smoked fish or cold roast poultry, pork, or beef. Or try the garishly gorgeous combination of snappy onions and melting avocado in salads or sandwiches.
For pretty slices that hold their shape, choose onion bulbs about two inches in diameter—preferably a red variety. Long large shallots or elongated red onions can also be used. Narrow white onions are fine too, but you’ll want to add more beet for color.