Add the tomatoes and oats in a blender and make a fine puree

Heat oil and add the asafoetida and mustard seeds. Allow the seeds to splutter

Add the semolina now and sauté for 2-3 minutes until light brown on Low heat

Add the tomato-oats purée, salt and mix well

Take off heat and let the mixture rest covered for 15 minutes

Pour required amount of water into a steamer/idli steamer

Grease the idli trays and fill them up with the tomato-oats-semolina batter

Steam cook first 5 minutes on high and then for another 7-10 minutes on Low heat

Check if the Idlis are ready before taking off heat

Let the Idlis cool slightly before demoulding

Serve warm with your favourite chutney and sambar