PreparationFor onions: Position rack in center of oven and preheat to 425°F. Line large rimmed baking sheet with foil. Whisk first 6 ingredients in large bowl. Add onions; toss gently. Arrange onions close together, 1 cut side down, on baking sheet; spoon juices from bowl over. Roast 30 minutes. Using small spatula, carefully turn onions over. Continue to roast onions until tender and thickly coated with glaze, watching to prevent overbrowning, 25 to 28 minutes longer. Remove from oven. DO AHEAD: Can be made 3 hours ahead. Let stand on baking sheet at room temperature. Rewarm in 350°F oven before serving, if desired. For gremolata: Mix pomegranate seeds, parsley, and orange peel in small bowl. Arrange warm or room-temperature onions on platter. Sprinkle gremolata over and serve.
PreparationFor onions: Position rack in center of oven and preheat to 425°F. Line large rimmed baking sheet with foil. Whisk first 6 ingredients in large bowl. Add onions; toss gently. Arrange onions close together, 1 cut side down, on baking sheet; spoon juices from bowl over. Roast 30 minutes. Using small spatula, carefully turn onions over. Continue to roast onions until tender and thickly coated with glaze, watching to prevent overbrowning, 25 to 28 minutes longer. Remove from oven. DO AHEAD: Can be made 3 hours ahead. Let stand on baking sheet at room temperature. Rewarm in 350°F oven before serving, if desired. For gremolata: Mix pomegranate seeds, parsley, and orange peel in small bowl. Arrange warm or room-temperature onions on platter. Sprinkle gremolata over and serve.