- *** please note that the measurements are just approximations. ***
Chop tomatoes to small pieces and cook them in about 250ml of water and turmeric powder. 
- Grind coconut, mustard seeds, red chillies with  2 to 3 tblsp of yogurt and a little water, to a fine paste. make sure that the paste is not very watery. 
- Once the tomotoes are cooked, add the ground paste, remaining yogurt, salt to taste and the sugar. You may add some water to the mixture if the consistency is thick. 
- When the mixture starts to boil, remove from heat. 
- Season with mustard seeds and curry leaves. 
- Serve with rice. 
- ** you may use fresh cucumber instead of tomatoes. in that case do not cook cucumber in water and turmeric powder. make a fine paste of coconut, green chillies, mustard seeds - mix with yogurt - add the cucumber and salt.  this tastes fantastic with hot puris. **