Set the grill to high. Spray the grill rack with oil.
Mix the salt, pepper, and Cajun spice mix to make the seasoning. Set fish aside on a plate.
Heat the butter in a small saucepan over medium heat, add the lemon juice and spring onion. Cook until the onion is soft, around 3 minutes.
Spray the cod fillets lightly with oil. Place the fillets skin side up on the oiled grill.
Coat the fillets with the butter mixture while grilling.
Grill them until you can smell the fish’s aroma, for about 3 to 4 minutes.
Flip the fillets and sprinkle seasoning on top of the fillets.
Cook for another 3 to 4 minutes, and take the fillets off the grill. This makes each side have a chance to absorb flavour.
Serving Suggestions: Serve with a lemon wedge and French bread.