Ingredients:

Tomatoes ½ kg
Red chillies 6 to 8 nos
Tamarind lemon size
Salt as per taste
Asafoetida ¼ tsp
Mustard seeds 1 tsp
Vendhayam ¼ tsp
Gingelly oil 6 tblsp
Turmeric powder ¼ tsp

Method

Grind tomatoes, tamarind, red chillies and salt.
Heat oil in a kadai.
Add mustard seeds, asafoetida, vendhayam and turmeric powder.
Pour in the ground tomato pulp. 
When the gravy becomes thick remove from fire.
Serve hot with idlis, chappathis, dosa and rice.