Blanch the tomatoes in a big bowl of water, make slight incisionson one side of the tomatoes so it is easier for you to peel them later. Boil till the skin starts cracking up, this will take about 6-8 minutes.
Remove the tomatoes and dip them in cold water and retain the water in which you boiled it.
Remove the skin of the tomatoes and puree them well. My house help from Dharward tells me that they just hand mash the tomatoes and that is the best way to make the saar so I follow the same.
Heat oil in a pan and add the jeeera seeds and fry till they turn slightly brown, add the curry leaves and mashed tomatoes. Fry for another 2 minutes.
Add salt, jeera powder, tamarind or lemon juice and 2 cups of water.