Agrodolce onions, the classic Italian antipasto, are usually made with cipollini—small, flat, disc-shaped onions lacquered in a sweet-sour glaze. We wanted a more substantial side dish, something that could stand alongside a Thanksgiving turkey or rich roast.

The answer was to think big—large yellow or sweet onions cut into hefty wedges. We left the root ends more or less intact, which held the layers together so the wedges didn’t fall apart during cooking.

We started with a classic onion tarte tatin in mind—onion wedges tessellated in a skillet and cooked until caramelized, then flipped onto a platter. The idea was to save room in an already taxed oven. But the flip was both awkward and perilous so we went with an 8-inch square baking dish that could go straight from oven to table.

Getting the onions tender was the tricky part. We tried a straightforward roast at 400°F, uncovered, but even after two hours, they were dried out and fibrous, not jammy and succulent. They were losing too much moisture, leaving behind onion carapaces.

The breakthrough came when we split the cooking into two stages. We arranged the wedges snugly and covered the dish tightly with foil. The foil trapped the steam, helping the onions soften without drying out. About 45 to 50 minutes got them tender but not quite finished. We removed the foil and returned the baking dish to the oven, turning it up to 425°F—the extra heat browned the onions and concentrated the moisture in the dish into a light glaze.

Yellow onions worked better than red—jammier, softer and more forgiving. Sweet onions also worked. The red had a tendency to stay more fibrous and the pigments shifted to a washed-out hue. For the agrodolce (literally, sour-sweet) we used sherry vinegar rather than the more common balsamic or wine vinegar. The sherry vinegar’s rich, nutty character added depth. We used honey for sweetness and butter and fresh thyme to tie the sweet and sour elements together.

These onions are good warm or at room temperature—they can wait while the turkey rests and the meal comes together. They can also be made through the covered stage up to two days ahead, leaving just the roasting and glazing stage.

Michelle Locke

Michelle Locke is a writer and editor with 25+ years of experience in media and communications. As books editor at Milk Street, she specializes in helping shepherd projects from concept to completion and is known for her dogged, some say relentless, attention to detail. Michelle has a degree in journalism from the University of Texas at Austin. When not updating spreadsheets she spends her time reading, walking and doing laundry.