In a wide mixing bowl add chopped tomatoes, salt, Chilli powder and pinch of turmeric powder
Grind them without adding water Add oil to the pressure cooker when oil is hot add mustard seeds and let it splutter
Add the blended purée and cook for about 1 minute till they start bubbling
Cook for 25 - 28 whistles for 25 minutes and let the pressure settle down
Open the cooker and mix well
Depending on the tomatoes variety it will be watery
Add jaggery and mix well
When thokku comes to your desired consistency add fenugreek powder and mix well
Switch off and let it cool down
Store it in a airtight container