Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Rinse the quinoa thoroughly in a fine-mesh sieve, then place it in a small saucepan with 0.5 cup of water. Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes.
While the quinoa cooks, trim the woody ends off the asparagus spears and place them on one side of the prepared baking sheet.
Place the salmon fillet on the other side of the baking sheet.
Mince the garlic clove and whisk it in a small bowl with the olive oil, dried oregano, sea salt, and black pepper.
Drizzle the herb oil mixture over both the salmon and the asparagus, using a brush or clean hands to ensure the salmon is well-coated and the asparagus is tossed evenly.
Roast in the oven for 12 to 15 minutes, or until the salmon flakes easily with a fork and the asparagus is tender and slightly charred.
Remove from the oven and squeeze the fresh lemon juice over the salmon and vegetables.
Fluff the cooked quinoa with a fork and serve it as a base for the roasted salmon and asparagus.