1. Heat oil in a soup pot and saute onions for 5 minutes.
2. Add garlic and ginger and saute 5 more minutes.
3. Add spices and salt, saute 5 minutes more.
4. Add 4 cups of water and stir. Add tomatoes and lentils. Bring to a boil and then lower the heat a bit and simmer for 20 minutes.
5. Add the lemon juice and cilantro and more water if it's too thick. Simmer 10 more minutes, or until lentils are completely tender. This may take a while.