Soak a large lemon size ball of tamarind in hot water and squeeze out the extract and keep aside.
Fry the ingredients mentioned (menthiyam, jeeragam, and sesame) together and grind it into powder once cooled.
Heat a saucepan and add oil. Once the oil heats add the ingredients mentioned under seasoning and fry for a minute.
Now add the chopped onions along with turmeric powder and sauté for about 5 mins. Now add the ginger-garlic paste and fry for a couple of minutes more.
Next, add the chopped eggplant and sauté for about 5 mins or until slightly softened.
Next add the tomatoes, green chilies, dhania powder, chili powder, and salt. Mix everything well and fry for 5 more minutes.
Now add the tamarind extract and vinegar. If the kuzhambu appears too thick, add about ½ cup of water and let it boil. Add the curry leaves too at this stage.
Let the mixture boil for about 15 minutes or until the raw smell goes. Now add the ground powder and let it come to boil once.
Turn off the flame and serve hot with rice.