Heat oil in a pan. Add mustard seeds and let them pop, add the split gram dal and let it turn red. Add the curry leaves, red chillis and asafoetida and toss for a few seconds.
Add the chopped onions and green chillis and fry till transparent. Add turmeric pwd and salt.
Add the chopped tomatoes and cook for 6-8 mts or till they turn soft but not mushy. Turn off heat and cool.
Beat the curd till smooth. Combine the cooked tomato mixture with the beaten curd and garnish with fresh coriander leaves. Serve with white rice or rotis.