Clean the fish well; remove the insides leaving the head and tail intact. Score on both sides.
To prepare the spice blend, dry roast the coriander seeds and fennel seeds till fragrant and aromatic. Allow to cool.
Grind the coriander seeds, cumin seeds, bay leaf, dry red chillies, cinnamon and ajwain to a fine powder.
To this add amchoor, garlic cloves, turmeric powder, besan, lemon juice and enough water to grind to a thick paste like consistency.
Season the fish with salt and rub the spice blend all over, especially the insides of the fish. Marinate for at least 4 hours or as long as possible (keep refrigerated).
Allow to come to room temperature before grilling.
Pre heat the oven to 200°C. Line an oven proof tray with baking paper and place the fish. Drizzle lightly with oil and grill for 25 minutes. Remove and turn the fish over; drizzle lightly with oil again and grill till done.
Serve warm garnished with coriander leaves and lemon wedges on the side.