Sautee onions and garlic in oil in 3 quart saucepan over med. heat until onions are tender. Stir in water (or stock), salt and lentils. Heat to boiling; reduce heat. Cover and simmer 1 hour. Stir in lemon peel, lemon juice and spinach. Cover and simmer until spinach is tender, about 5 minutes. A serving is about 1 1/4 cup.