In a bowl, mix together onion, tomatoes, green chilies and coriander leaves. Keep aside. Heat 1 tsp. oil in a non-stick pan and drop a small ladleful of the batter.
Sprinkle some of the onion mix over it and fry on a medium flame for a minute or two. Flip it over and let it cook further for a minute.
Transfer to a serving plate. Make similar uttapams with the remaining batter. Serve them with coconut chutney and sambar.