Soak rice and millet overnight or at least for 6~8 hours.
Drain the water and grind rice & millet along with grated coconut, dried red chilies, tamarind and salt to a smooth batter. Add enough water to make a pourable batter.
Stir in cabbage, onion and cilantro. Mix well.
Heat a griddle/ tawa on medium-high heat. Pour a ladleful of batter in a circular manner. Batter doesn't spread quite as much as regular dosa batter, so don't try too hard to get perfect circles.
Drizzle oil on top and cook dosa till golden on one side, about 2~3 minutes. Gently flip the dosa and cook on the second side for another 1~2 minutes. Repeat with the remaining batter.
Serve hot with your favorite chutney or just as is.