In a small bowl, whisk together the lemon juice, lemon zest, minced garlic, dried oregano, and half of the olive oil.
Place the salmon fillet in a shallow dish, coat thoroughly with the marinade, and let it rest for 10 minutes.
Toss the asparagus spears with the remaining olive oil, sea salt, and black pepper until evenly coated.
Preheat a grill or grill pan over medium-high heat.
Grill the salmon for 4 to 5 minutes per side until the center is opaque and the fish flakes easily with a fork.
Grill the asparagus for 3 to 5 minutes, turning frequently until tender and slightly charred.
Serve the salmon immediately alongside the grilled asparagus, drizzling any remaining pan juices over the top.