Heat oil or ghee in large saucepan; add onion and sauté until softened, about 5 minutes. Stir in turmeric, ginger and crushed red pepper and sauté another minute. Add spinach, tomatoes and water; bring to a boil. Reduce heat, cover and simmer about 15 minutes. Add lemon juice and salt to taste.
Note: if desired, cool the dish slightly and puree before adding lemon juice. Bring the puree back to serving temperature, add lemon juice and salt and serve.