Soak rawa in curd and 1 cup of water. It should be a thick pourable batter. Rest it for 2 hours.
Mix salt, baking soda, baking powder in rawa batter. Rest for half an hour more.
Fill batter in greased idli moulds.
Take out thin slices of a tomato.
Place one tomato slice over each batter filled cavity of mould.
Steam Idlis for 12-15 minutes.
Puree two tomatoes.
In a wide non stick pan Crackle mustard seeds in oil. Add curry leaves.
Add ginger paste. Saute.
Add pureed tomatoes with salt and red chilli powder. Cook till oil oozes out.
Add chilli flakes and oregano. Cook for few seconds.
Add 1/4 cup of water. Give a boil.
Add tomato ketchup and vinegar. Mix.
Place cooked Idlis over tomato curry and cook for a minute.
Flip and cook for another minute.
Serve hot with coconut chutney.