Rinse and drain lentils. In an electric crockery cooker combine lentils, water, onion, celery, carrot, bouillon granules, garlic, lemon peel, and red pepper.
Cover and cook on low-heat setting for 7 to 8 hours. (Or, cook on high-heat setting for 3-1/2 to 4 hours.) Add ham. Cook, covered, on high-heat setting for 10 minutes more. Stir in spinach; serve immediately. Makes 4 to 6 servings.