Mix rice flour, maida and rava with salt. Add enough water to make a thick batter without forming lumps.
Add chopped onion, cilantro and green chillies, add more water and make a thin batter of buttermilk consistency.
Heat oil in a pan and add cumin seeds. Fry for about 10 seconds till nice aroma comes out. Pour it over the dosa batter and mix well.
Heat a pan. Pour a laddle full of batter in a circular motion and make the dosas. Add very little oil and fry till golden.
Turn over and fry for another minute.
Serve hot with chutney.

Method of making chutney:

Combine coconut, green chilli, red chilli, ginger, and tamarind paste and salt in a mixer and grind to a smooth paste by adding enough water.
Heat oil in a pan and add mustard seeds. When they splutter, add curry leaves. Pour this over the ground paste and mix well.
Serve with dosa. (This chutney goes well with any dosa).