Soak lentils in enough water to cover for 2 hours.
Drain and combine in a saucepan with 6 cups water and turmeric.
Bring to a boil. Reduce to a simmer and cook for about 20 minutes, until lentils are cooked through.
In a large pot, heat ghee.
Add asoefetida and cumin seed.
Fry for 1 minute until cumin seed starts to tast a little.
Add ginger garlic paste and fry for 30 seconds.
Add onion and saute until softened.
Add tomatoes, coriander and chillies.
Cook for about 5 minutes, 1 minutes if using canned tomatoes.
Add cooked lentils with all of the cooking liquid.
Using a potato masher, mash the lentils until they are 50% mashed.
Add salt to taste and simmer for 10-15 minutes. The longer you cook, the thicker the dal will become. If you prefer thinner dal, simmer for less time.
Serve with rice or flatbread.