Soak the black gram for 4 hours.
Add the soaked lentils to a blender and blend until smooth paste till dosa batter consistency. Add water as required. Make sure it is not runny.
Add rava and mix well. The consistency of the batter should be now thick.
Set aside for 1 hour.
Add cumin and salt. Mix well.
Take a heavy bottomed pan and add 1 tbsp oil.
Pour the batter into the pan and see that the thickness is around 1 and half inch.
Cover the pan with a lid and cook until the batter gets firm.
Fry without lid, until even crust forms on the base. Flip it to get the same on the other side.
Switch off the fame and leave it in for 2-3 min.
Cut it into 4 pieces with a knife. Serve hot with any chutney or pickle.