Wash and clean the fish with water and remove the scales and backbone carefully.
Marinate the fish with mustard paste, yoghurt, salt and turmeric for at least 10 minutes.
Cook the fish in a tandoor or on a stovetop on medium heat.
When the fish turns pale and is cooked from the inside (not raw), make slices in at least 3-4 places along the sides and remove the steam from the inside.
Apply some mustard oil on top and squeeze lemon juice on top and serve.
Serving Suggestions: Serve with onion rings and lemon wedges. You can also serve it with sticky rice or dosa.