Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
In a small saucepan, combine the quinoa with 0.5 cup of water. Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes until the water is absorbed and the quinoa is fluffy.
Trim the woody ends off the asparagus and place them on one side of the prepared baking sheet. Place the cod fillets on the other side.
Drizzle 0.5 tablespoon of olive oil over the cod and asparagus, then season both with sea salt and black pepper.
Bake in the oven for 12 to 15 minutes, or until the cod is opaque and flakes easily with a fork and the asparagus is tender-crisp.
While the fish bakes, prepare the gremolata by finely chopping the fresh parsley, mincing the garlic, and zesting the entire lemon.
In a small bowl, combine the parsley, garlic, lemon zest, and the remaining 0.25 tablespoon of olive oil.
Divide the cooked quinoa between plates, top with the roasted asparagus and cod fillets, and generously spoon the fresh gremolata over the fish before serving.