Balsamic Red Onions

Heat broiler, with rack in top position. On a rimmed baking sheet, place red onions in a single layer and drizzle with olive oil, turning to coat with oil. Season with salt and pepper. Broil onions until lightly charred, 4 minutes. Flip and brush with balsamic vinegar. Broil until lightly charred, 4 minutes. To serve, transfer to a platter and sprinkle with parsley. Serve warm or at room temperature.