1.Preheat oven to 240°C/220°C fan-forced.
2. Brush base of baking dish with half of the oil, add beetroot; cover tightly with foil. Roast 45 minutes.
3.Combine onions with remaining oil, add to beetroot; cover tightly with foil. Roast 30 minutes or until vegetables are tender. Remove foil; roast further 10 minutes.
4.Wearing rubber gloves, remove skin from hot beetroot; cut beetroot in half.
5.Place beetroot and onion in serving dish; drizzle with combined vinegar and extra oil, sprinkle with parsley and freshly ground black pepper.