Pre heat the grill to its highest setting.
Pat the cod fillets dry, removing as much moisture as possible with kitchen towel.
Put the low carb roll in a food processor and process into breadcrumbs, hten transfer to a small bowl.
Add the chopped coriander, cayenne, lime zest and cheddar and season with salt and pepper. Mix well.
Line a baking tray with foil, dull side up. Grease with a little butter or olive oil.
Place the fish fillets on the foil.
Spread enough tartare sauce over to cover the fillets.
Spoon on the crumb mixture, dividing it equally between the 4 pieces.
Drizzle with olive oil and place under the grill, as low as it will sit away from the direct grill element (or it will burn the crumb).
Depending on the thickness of the fish, grill for 8 - 15 minutes.
Serve with mixed salad leaves, lime and coriander tartare sauce and lime to squeeze.