In a large mixing bowl, combine 1 cup sooji (semolina), 1/2 cup rice flour, and 1/4 cup all-purpose flour (maida).
Gradually add 2 1/2 cups of water while continuously whisking to avoid lumps. The batter should be thin and flowing.
Add 1/2 cup finely chopped onions, 1/4 cup chopped coriander leaves, 1/4 cup grated coconut, 2 finely chopped green chilies, 1 tsp grated ginger, 1 tsp cumin seeds, and salt to taste. Mix well and let the batter rest for 15-20 minutes.
Heat a non-stick tawa or dosa pan over medium heat. Sprinkle a few drops of water to check if the pan is hot enough. If the water sizzles and evaporates, the pan is ready.
Stir the batter well and pour a ladleful onto the hot tawa, spreading it in a circular motion to form a thin, lacy dosa. Drizzle 1 tsp of oil or ghee around the edges.
Cook the rava dosa until the edges turn golden brown and crispy. Gently flip it over and cook for another 1-2 minutes.
Fold the dosa and transfer it to a serving plate. Repeat the process with the remaining batter.