Put the onion wedges in a bowl of ice water and soak for about 2 hours.
Drain in a colander for 10 minutes.

Preheat the over to 400 degrees F. Arrange the onions on an oiled baking dish.

Whisk the vinegar and honey together, and season with pepper. Pour over the onions, tossing gently to coat. Drizzle the onions with the olive oil.

Cover with foil and bake for 25 minutes. Uncover and bake an additional 45 minutes, or until tender.