We wondered whether you could caramelize onions on the grill. The answer: You can. While we normally prefer not to grill in foil packets, the foil is a necessity for this recipe. It traps the juices and keeps the onions moist. First we grill slices of onion to lightly char them. Then we break the charred onions into rings and sprinkle them with salt and sugar to help draw out the moisture. When wrapped in foil and returned to the grill, the onions soften in texture and deepen in sweetness. Serve them as a side dish or in a sandwich.
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Add a splash of balsamic vinegar to the foil packet before sealing and finishing grilling.
Replace the Vidalia with any sweet onion, such as Maui, Walla Walla, or Texas sweet onions.
When skewering the onion rounds, push the skewer across the grain of the rings to make sure the rounds will hold together on the grill.
To keep the onions flat on the grill, put the skewers directly on the grill rather than hanging off the edge. Wear heat-proof gloves when turning the skewers.
Heat the Grill as Directed.
Slice the onion into rounds about ¼ inch thick. Skewer the rounds through the side so that they will lie flat on the grill. Generously coat them all over with oil.
Brush the grill grate and coat it with oil. Put the onion rounds on the grill directly over medium-high heat until nicely grill-marked, 2 to 4 minutes per side. Rotate the onions 45 degrees halfway through the cooking on each side to create crosshatch marks and more even browning.
Put the browned rounds on one side of a large piece of foil. Cut each round in half crosswise, if you like. Break the onions into rings with tongs and arrange them in a single layer. Sprinkle all over with the salt and sugar, and spray or drizzle with a bit more oil. Fold the foil over the onions and crimp to seal. Reduce the heat to medium-low (on a gas grill) or put the foil over the medium-low-heat area (on a charcoal or wood grill). Cover and grill until the onions are very soft, 10 to 15 minutes, turning the sealed packet once or twice. Let rest, wrapped in foil, for 5 minutes before using.