Marinate the fish steaks with 1/2 tsp salt and 1/2 tsp turmeric powder and keep aside.
Heat 2 tbsp of mustard oil in a large pan and fry the fish lightly until golden brown. Drain and keep it aside.
Add the rest of the oil to the same pan and heat. Once hot add dried red chilli and nigella seeds.
When the nigella seeds splatters add the chopped garlic and fry for 4-5 seconds.
Then add in the chopped tomatoes and sauté until the tomatoes are soft and mushy.
Now add the turmeric powder, chilli powder, salt, sugar, green chillies and coriander leaves. Mix everything well.
Simmer for 7-8 minutes or until you see the oil seeping through the masala.
Now add a cup of water and bring it to a boil. Then slowly slip in the fried fish and simmer for another 4-5 mins.
Sprinkle with some fresh coriander leaves and enjoy it with hot rice.