Heat oil/butter/ghee in a pan and temper mustard seeds and cumin seeds. Once they crackle, add chana dal and urad dal. Fry them till they turn golden. Then add the chopped green chillies and curry leaves. Fry for a minute and then add chopped onions. Saute till they turn translucent.
Now add turmeric powder, chilly powder and salt. Saute for 30 seconds and then add the chopped tomatoes. Continue to cook the tomatoes till they turn pulpy. Then add the cooked rice. Mix it all together and cook for a minute or two. Lastly garnish it chopped cilantro.
Serve it warm along with some raita or plain yogurt.