first make dosa batter.
you can also use leftover dosa batter.
mix the chopped onions, tomatoes, green chili, coriander together in a bowl.
heat a griddle or non stick tava. take 1 ladle of uttapam batter and spread it in a circle on the tava similar to the way you would make a dosa. only the quantity of batter will be more than what you would normally use for a dosa. the uttapam should be thick.
top the uttapam with the onion, tomatoes and chili mixture.
sprinkle a bit of pav bhaji masala or sambar masala or idli podi and salt on top of the veggies and uttapam.
add some ghee or butter on the sides and top of the uttapam.
turn the uttapam when the base is cooked. apply some ghee/butter on the cooked side.
the onion tomato side is getting cooked now. flip when this side also gets cooked.
flip again if you see the first side is not cooked or browned.
when the uttapams are crisp and cooked on both sides, then serve the uttapams hot with hot sambar and coconut chutney. you could also serve uttapams with curd chutney or simple sweetened or plain curd.
serve onion tomato uttapam hot to have best taste.