Remove the skin/scale of the fish, wash thoroughly and cut into pieces if its large fish or leave as it is.
Add red chilly powder, turmeric powder and salt into the cleaned fish. Pour 1 cup tamarind water, mix well and keep aside.
In a deep bottomed pot (preferably clay pot) heat oil and splutter mustard seeds and then add fenugreek seeds, crushed ginger-garlic and fry it.
To this add the sliced tomato and green chilly.
Saute till it becomes soft.
Now pour the masala water without adding fish.
Cover and bring it to boil for 8-10 minutes.
Finally add the fish and cook for 4- 5 minutes in medium flame.
Add curry leaves and remove it from the flame.
Sour and Spicy Sole fish curry is ready now.