Heat 2tbsp oil in a sauce pan; fry the vadiyalu until golden. Remove and set aside.
In the same pan, add the tempering ingredients and once the seeds start to splutter, add the chopped onions and green chilies. Cook until the onions are translucent, about 3-4 minutes.
Next add tomatoes and cook covered until they turn mushy. Add 2cups of water, tamarind paste, sambar powder, salt and jaggery. Bring the mixture to a boil and simmer for 4-5 minutes.
Finally just before turning off the stove, add the fried vadiyalu and chopped cilantro. Serve with steamed rice and a dry curry for a filling meal.