Soak daal overnight.
Cook it in a pressure cooker.
Heat oil in a pan or a kadai.
Fry onion, until it becomes golden brown.
Add green chillies and tomatoes and saute.
Add the cooked daal and a little water, if necessary.
Add salt and mix well.
Add turmeric powder and sambar powder.
Stir well and allow it to boil.
Turn off the flame.
Add coconut milk and stir well.