Available in red or yellow varieties, cipollini onions have a baby, round, flattened onion shape and are typically 1-3 inches in diameter with skins that are paper thin. These bulbs are sweeter than standard yellow and white onions but don't have quite as much sugar as a shallot. They can be roasted and used as you would caramelized onions. They are imported from Italy and are available year-round.