At Azhagar Kovil dosai is the prasadam offered to god. It's a temple near Madurai. Happened to come across this recipe in Aval Vikatan.
What you need:
Whole black gram (with skin) - 1/4 cup
Raw rice -1 cup
Coconut Gratings - 1/4 cup
Salt - 1 tsp
Sesame oil as reqd
Wash and soak rice and black urad separately overnight.
Grind dhal and rice seperately to smooth texture. Add coconut, salt mix the batter and let it ferment overnight or for 8 hrs.
Heat dosa tawa pour batter, spread it evenly and add sesame oil around the dosa turn over and cook until done.