Cooking these slightly sharp-flavored onions agrodolce style (in a sweet-and-sour sauce) turns them into meltingly sweet little morsels. They’re substantial enough to work on their own as a side to your next roast, and the leftovers are tasty when rewarmed, chopped coarsely, and tossed with mixed salad greens for something akin to a warm bacon vinaigrette.
What to buy: Cipollini are small, flat red or yellow onions, commonly seen in markets from late fall through winter.
Game plan: To make cutting the bacon easier, chill it in the freezer about 20 to 25 minutes until it firms up.
1Heat the oven to 450°F and arrange a rack in the middle. Combine onions, bacon, and olive oil in a 13-by-9-inch baking dish, stir to coat onions in oil, season with salt and freshly ground black pepper, and place in the oven.
2Roast, stirring occasionally, until onions are golden and start to become tender, about 30 minutes. Meanwhile, combine remaining ingredients in a small saucepan over medium heat, stir until sugar is dissolved, then continue cooking until reduced by 1/2, about 20 minutes.
3When onions are done, remove from the oven, pour sauce over them, reduce oven temperature to 400°F, and return the baking dish to the oven. Roast onions, basting occasionally, until sauce is thick and syrupy, about another 8 minutes. Remove from the oven and stir onions to coat in sauce. Return to the oven and continue roasting until fork tender, about 8 minutes more. Serve hot or lukewarm.