Pat the cod dry with a paper towel. Sprinkle with the Cajun seasoning and sea salt and let stand 30 minutes at room temperature.
Make 4 tinfoil packets by place two pieces of tinfoil on top of each other, placing one cod in the center of each. Drizzle each fillet with 1 tsp of olive oil and close the packets very tightly.
Place the packets on the grill, folded side up, and grill until the fish is opaque and flaky, about 5-10 minutes depending on the size and thickness of the fillet. Once cooked, set aside to rest and cool for 5 minutes.
While the fish cools, mix all the slaw ingredients including the apple cider vinegar, up to the parsley in a large bowl. Stir in the parsley.
Add in the vegetables and stir until they’re well coated.