Take the fermented dosa batter.
Add salt as per requirement into the batter, mix well.
Heat the dosa tawa, wipe the tawa with an onion slice, take a ladle full of dosa batter, spread the dosa batter on the tawa in circular motion.
Beat egg on the dosa, spread the egg mixture all over the dosa.
Spread some chopped onions all over the dosa, spread some chopped tomatoes over the dosa, spread some coriander leaves all over the dosa.
Add some chopped green chillies as an optional ingredient.
Sprinkle salt all over the dosa.
Smear oil all over the dosa corners and on the dosa.
Cook the bottom side well and also the egg on the top too should be cooked well on medium flame to low flame.
Once done, fold the dosa and take the dosa out of the plate.
Serve hot with any dosa chutney.