Preheat your oven to 400°F (204°C) and lightly grease a large baking sheet with olive oil.

Zest one lemon and thinly slice half of it; set aside both the zest and the lemon slices.

In a large bowl, combine asparagus, cherry tomatoes, bell pepper, red onion, and olives. Drizzle with olive oil, then sprinkle with sea salt and black pepper. Toss well and spread evenly on the baking sheet.

Pat the cod fillets dry with paper towels and nestle them among the vegetables on the baking sheet, seasoning with sea salt and pepper.

Bake for 15 to 18 minutes, until the cod flakes easily and reaches an internal temperature of 145°F (63°C) and the vegetables are tender.

Remove from oven and sprinkle with additional chopped parsley. Serve alongside lemon risotto or roasted potatoes.