Bring 2 1/2 cups of water to a boil over high heat. Add the cup of rice, cover and let simmer over medium heat for 35-40 minutes until all the water is absorbed and the rice is cooked. Remove from heat and let cool.
If using white basmati rice, follow the same procedure, just use 1 1/2 cups water per cup of rice and simmer for 20-22 minutes to cook completely.
Melt the butter in a non-stick pan over medium-high heat. Add the mustard seeds and asafoetida. As soon as they start spluttering add garlic, ginger and green chillies.Fry for a minute, add the onions and turmeric powder.
When the onions start turning golden brown, add the tomatoes, salt and coriander powder. Mix well, cover and cook over medium heat for 8-10 minutes. Uncover, add the cilantro and stir together.
At this stage, this makes a great side dish on its own, served with chapathi or naan.
Add this tomato-onion mixture to the cooked rice, mix well together and serve warm.