Wash the tomatoes and blend into a smooth puree. Keep aside.
Heat 1 tsp ghee in a pan.
Add mustard seeds, udad dal, chana dal andcurry leaves. Saute for few seconds.
Add rava and saute on slow flame.
Roast the rava till it turns aromatic. Turn off the flame and allow the rava to cool.
In a mixing bowl, add the roasted rava,curds, tomato puree and mix. Keep this mixture aside for 30 minutes.
After 30 minutes, add water as required, to get the desired consistency. Mix well.
The batter should not be too thin or too thick.
Add salt, fruit salt (eno) to the mixture and give a quick mix.
Grease idli plates with oil and pour the batter into idli moulds.
Steam the idlis for 10 to 15 minutes or till the idlis are cooked.
Unmould the idlis and serve hot with chutney and/or sambar.