A simple but flavourful fish curry is your answer to curry night in a flash. This authentic fish curry from Goa includes a homemade coconut-based curry paste.
Kokum is made from dried mangosteen peels and used in some Indian regional cuisines to add a sour flavour. Tamarind works just as well, and may be easier to find.
For a creamier, richer curry, you can use coconut milk instead of water. Add enough till your desired consistency is reached.