Heat 2 tablespoons of oil and saute the onion for a few minutes. Add and mix it in idly batter with salt.

If batter is too thick add some water. Heat the dosa pan, spoon some oil and ladle batter on the dosa pan(slightly spread it in a round shape and cook in medium heat).

When the sides of dosa turns golden brown, turn it and cook for a few minutes. Serve it with chutney and sambar.