Soak urad dal and rice separately for at least 6 - 7 hours.
Grind the urad dal with minimal water in a mixer to make a smooth paste and rice into a coarse paste
Mix the two and let it ferment for about 6 - 7 hrs
Grind the batter into a fine smooth paste
Heat a pan before frying the uttapam and once its hot bring it off the flame
Spread the batter on the pan using a spoon in a circular motion
Put it back on the flame and cook it on medium flame
Before the batter dries out a little brush some oil on it and very quickly add chopped onions, chopped tomatoes, capsicum, green chillies, coriander leaves.
Sprinkle little salt to it
Flip it over and cook the other side as well.
Cook evenly and the uttapam is ready to be served