First, soak the tamarind with hot water in a bowl.
Take a bowl, add the fish pieces along with salt, turmeric powder and chilli powder. Mix well and keep aside.
Next heat a small pan and roast the ingredients mentioned above except garlic pods on low - medium flame until they change their colour slightly or until you get a nice aroma.
After that transfer them into a blender and add garlic pods and grind them into a smooth paste by adding little water.
Now heat a wide pan with oil, once it is hot enough add cumin seeds and allow it to crackle. Then add chopped onions, slit green chillies, turmeric powder and curry leaves.
Sauté well until onion changes its colour. Add ginger-garlic paste and sauté until the raw smell goes out.
Then add chopped tomatoes and sauté for few minutes. After that close the pan with a lid and cook until the tomatoes become soft and mushy on medium flame.
Now add the ground masala and cook until the oil oozes out from the masala. Add red chilli powder, tamarind juice and required water and bring it to boil for few minutes.
Cover and cook for 5-8 minutes on medium flame. Open the lid and mix well. Slowly add the salmon pieces and rotate the pan slowly in a way that the fish is nicely coated with the masala.
Again cover and cook for 5-8 on medium flame. Don't use any spatula otherwise fish will break. Simply rotate the pan. Once the fish is cooked, add finely chopped coriander leaves and switch off the flame.
It is best to serve after 1-2 hours.