To begin, prepare the curry powder. Dry roast coriander seeds (dhania), cumin seeds (jeera), fennel seeds (saunf), Kashmiri red chillies, fenugreek seeds (methi dana), mustard seeds (sarson), black peppercorns, cinnamon, and green cardamoms seeds until aromatic. Cool and grind into a fine powder.
Remove to a bowl. Add garlic powder, ginger powder (sounth), and turmeric powder (haldi). Mix well. The curry powder is ready to use.
To prepare the fish, pat dry the fillets until they are completely dry.
In a dish, mix together 4 tsp curry powder, salt to taste, coarsely ground black pepper, and 1 tsp turmeric powder.
Coat the fillets in the spice mix until they are well coated.
Heat a non-stick pan or a tawa. Add a tbsp of oil and spread it evenly. Add in the fillets and cook on medium heat on each side until crisp. Around 2-3 minutes depending on the size.
Remove to a serving dish. Squeeze some lemon juice on top and serve hot.