Pat the fish dry and place on a plate. Put the garlic, chilli powder, turmeric, lemon juice in a bowl, season to taste, and mix well to combine the flavours. Smear the fish with this mixture and set aside to marinate for 30 minutes.
Preheat a grill to very hot and then lower to medium heat. Grill the fish for approximately 10 minutes on both sides until cooked through.
Serve hot with Indian bread or a rice dish.