Notes: If you have only one oven, roast the vegetables up to 1 day ahead; cover and chill. Let warm to room temperature to serve, or return to a 400º oven after the turkey is done; bake cold onions, uncovered, until warm, about 5 minutes. Squeeze the roasted garlic from peels onto potatoes or turkey.
5 or 6 onions (about 8 oz. each), unpeeled, rinsed
1 lemon (about 6 oz.), rinsed
1/4 cup olive oil
2 dozen large cloves garlic, unpeeled, rinsed
6 fresh rosemary sprigs (each 6 to 8 in. long), rinsed, or 2 teaspoons dried rosemary
About 1/4 teaspoon each salt and pepper
How to Make It
Cut onions in half lengthwise. Cut lemon in half lengthwise, then cut each half crosswise into 1/4-inch-thick slices; discard seeds and ends.
In a 12- by 17-inch baking pan, mix lemon, 1/4 cup water, olive oil, garlic, rosemary, and 1/4 teaspoon each salt and pepper. Spread level in pan. Lay onions, cut side down, in pan, on and around lemons and herbs.
Bake in a 400º regular or convection oven until onions are soft when squeezed, 50 to 60 minutes. Check occasionally; if pan juices evaporate before onions are tender, add a few tablespoons of water. Arrange onions, cut side up, on a platter; distribute lemon, garlic, and rosemary over onions. Serve hot or at room temperature. Add more salt and pepper to taste.