Soak long grain rice or dosa rice in hot water for 45 mins - 1 hour.
Drain the water from rice and rinse.
Grind the rice along with coriander seeds, cumin, red chillies, tamarind, and salt. Add water little by little while making the batter and make a smooth batter. Transfer the batter to a bowl, and then add water little by little to get a flowy batter.
Heat the pan. Let the pan be hot. Pour the batter from an inch above the pan.
Fill the pan completely with batter. A thin layer will be formed. Cover and cook for a minute
Grease the dosa, and flip it. Fold and serve with a vegetable gravy or chutney or jaggery syrup