Warning: The aroma while cooking these is intoxicating! Serve as a side with a hearty casserole, stew, or veggie omelet! Spanish inspired!
- Preheat the oven to 450*F.
- Cut the onions into halves at the equators.
- Remove the skin and any tough outer layers.
- Do not cut off the root and stem ends and be careful not to score the layers you don't remove: uncut, the outer layer will better hold the onion together as it roasts.
- Place the onion halves cut side down in a 9-inch square baking pan.
- Melt the butter in a saucepan and stir in the vinegar, thyme, salt, and pepper.
- Pour over the onions.
- Bake for about 20 minutes, and then turn the onions over and baste them with the pan juices.
- Bake for another 20 to 25 minutes, until easily pierced with a paring knife and the inner rings have begun to swell and rise up.
- Serve immediately or at room temperature.