In a large bowl, mix 1 cup ragi flour (finger millet), 1/2 cup rice flour, 1/4 cup urad dal flour, and 1/4 cup grated coconut. Add salt to taste.
Gradually add water to the mixture and whisk well to form a smooth, lump-free batter. The consistency should be similar to regular dosa batter (neither too thick nor too thin).
Allow the batter to ferment for 6-8 hours or overnight in a warm place.
Heat a non-stick tawa or dosa pan on medium flame. Once hot, pour a ladleful of batter onto the center of the tawa and spread it evenly in a circular motion to form a thin dosa.
Drizzle 1 teaspoon of oil or ghee around the edges of the dosa and cook until the bottom turns golden brown and crisp.
Flip the dosa and cook the other side for a minute or until it turns golden brown.
Fold the dosa and transfer it to a serving plate. Repeat the process with the remaining batter.
Serve the ragi dosa hot with coconut chutney, sambar, or any other accompaniment of your choice.