Bring water to a boil, add cipollini onions, reduce to a
simmer, cook until knife tender, about 15 minutes. Drain
well.
Heat a skillet over medium heat. Melt butter and
coat the onions entirely. Season with salt and toss until
caramelized, about 5 minutes.
Pour vinegar into the skillet and sprinkle sugar over
the onions. Bring to a boil, tossing until the sugar dis-
solves and the sauce thickens.
Serve hot or at room temperature.
