Clean and wash 500 grams of fish fillets. Pat dry and set aside.
In a bowl, mix 1 tablespoon ginger-garlic paste, 1/2 teaspoon turmeric powder, 1 teaspoon red chilli powder, 1 teaspoon garam masala, 1 tablespoon lemon juice, 2 tablespoons mustard oil, and salt to taste.
Add the fish fillets to the marinade, ensuring each piece is well coated. Marinate for at least 30 minutes.
Preheat your oven or tandoor to 200°C.
Place the marinated fish on a greased baking tray or skewer them if using a tandoor.
Bake or grill for 15-20 minutes or until the fish is cooked through and slightly charred on the edges.
Halfway through the cooking, brush the fish with a little mustard oil for extra flavor.
Garnish with freshly chopped coriander leaves and serve hot with slices of lemon and onion rings.