Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Trim the tough, woody ends from the asparagus spears and arrange them on one half of the prepared baking sheet.
Pat the cod fillets very dry with paper towels to ensure a clean sear in the oven and place them on the other half of the sheet.
In a small glass bowl, whisk together the olive oil, minced garlic, dried parsley, sea salt, and black pepper with the juice of half the lemon.
Drizzle the herb-garlic oil generously over the cod fillets and the asparagus, using your hands or a brush to coat the vegetables evenly.
Thinly slice the remaining lemon half into rounds and layer them over the top of the cod for extra brightness and moisture.
Roast in the oven for 12-15 minutes, or until the cod is opaque and flakes easily with a fork and the asparagus is tender with lightly charred tips.
Divide the warm cooked quinoa between plates and top with the lemon-herb cod and roasted asparagus, drizzling any remaining pan juices over the top.