1. Adjust oven rack to lowest position; remove remaining racks. Heat oven to 425 degrees. Following illustration below, line large V-rack with heavy-duty foil and poke holes in foil; set V-rack in 15- by 12-inch roasting pan.

2. Toss onions, carrots, celery, lemon, and thyme in medium bowl; set aside. Brush turkey breast with 2 tablespoons butter, then sprinkle with half of salt and half of black pepper. Set turkey breast-side down on V-rack. Brush with remaining 2 tablespoons butter and sprinkle with remaining salt and black pepper. Fill cavity with half of onion mixture; scatter rest in roasting pan and pour 1 cup water into pan.

3. Roast turkey 1 hour; remove roasting pan with turkey from oven. Lower oven temperature to 325 degrees. Using clean dishtowel or 2 potholders, turn turkey breast-side up; return roasting pan with turkey to oven and continue to roast until legs move freely and instant-read thermometer inserted into thickest part of thigh registers 170 to 180 degrees, about 2 hours longer. Transfer turkey to carving board and let rest, uncovered, 35 to 40 minutes. Carve and serve.

A V-shaped rack lifts the bird off the roasting pan bottom and ensures crisp skin. However, the bars on the rack will form ribbed impressions in the skin on the breast. To prevent this from happening, line the rack with foil and then use a paring knife or skewer to poke 20 to 30 holes in the foil so juices can drip down into the pan as the bird roasts.