In a dry large saucepan cook cumin seeds over medium heat for 3 to 5 minutes or until seeds are fragrant and toasted, stirring constantly. Stir in oil. Add tortilla strips, onions, and garlic. Cook and stir over medium heat for 5 to 6 minutes or until onions are tender.
Add stock, tomatillos, orange peel, and orange juice. Bring to boiling; reduce heat. Simmer, covered, for 30 minutes, stirring occasionally. Season to taste with salt and black pepper. If desired, sprinkle with cayenne pepper. If desired, serve with chopped tomato, sour cream, and/or toasted pumpkin seeds.