Combine all the ingredients in a mixing bowl, whisk well to form a lump less batter. Batter should be slightly more watery than pancake batter. Cover and set aside for at least 30 minutes.
When ready to make dosa, stir the batter well and add more water if the batter looks thick.
Heat a tawa/ griddle on medium-high heat for at least 5 minutes. Using a measuring cup or a small bowl, pour the batter from 3~4" above the pan in a circular motion. Fill the holes with more batter.
Drizzle oil over the dosa and cook on medium flame until the dosa is crispy, about 2~3 minutes. Flip over and cook for another 2 minutes. Serve hot with chutney.