Macher jhol, a Bengali fish curry that literally translates to Fish Gravy; my version is modestly spiced and served in a thick tomato-based gravy that tastes fantastic!
Heat a medium (24cm or 10") nonstick frying pan over a high heat. Add the oil when it is hot sear the cod loin pieces for a minute on each side.Then remove and set aside.
Add the cumin seeds, mustard seeds, and slit red chilli peppers to the frying pan.
When the seeds begin to crackle, add the curry leaves, garlic, and ginger and cook for 30 seconds.
Add the grated onion and cook for 7-10 minutes, stirring regularly until the onions go a fairly deep golden brown.
Add the tomato puree and cook for a minute ot two, stirring constantly.
Pour in the tomatoes, sprinkle over the sugar, ground coriander, ground turmeric and salt and stir.
Return the fish to the pan and coat well in the sauce, then add a lid and cook for 7-10 minutes, before serving.