In a pan add in water, Turmeric powder, salt, and bitter gourd. Cook until the bitter gourd is half cooked. Drain and set aside.
In a kadai add in oil. once it's hot add in Mustard, Jeera, and Fenugreek. Let it splutter and then add in the curry leaves and chopped shallots and fry for about 3 mins in medium flame.
Next, add in the tomatoes and cook till it is soft and leaves oil.
Next, add in the half cooked bitter gourd to the kadai and fry for a min. and then add Chilli powder, Sambar powder, Turmeric powder, and Salt and fry for about a min. . Check for salt and add as the bitter gourd is already cooked by adding salt.
Add in the tamarind juice extracted from the tamarind pulp. Cook for a min and then add in the Jaggery powder and mix well. Continue cooking until the kuzhambu thickens and leaves oil. Switch off the flame when it reaches the desired consistency.