Onion and Turkey Lime Salad

12 cups white or yellow onions, cut into narrow wedges
12 cups sweet red peppers, slivered
1⁄2 cup vegetable oil
12 cups cooked turkey, shredded
1⁄4 cup frozen grapefruit juice concentrate, thawed
2 tbsp. lime peel, grated
2 cloves garlic, crushed
4 tsp. ground cumin
3 tsp. hot red peppers, dried, crushed
1⁄2 cup lime juice
Lettuce as needed
Dairy sour cream as needed (optional)