Preheat your grill or a cast-iron grill pan to medium-high heat.
In a small mixing bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, dried oregano, sea salt, and black pepper.
Trim the woody ends off the asparagus spears and place them on a tray next to the salmon fillet.
Brush half of the lemon-herb marinade over the salmon and toss the remaining half with the asparagus until evenly coated.
Place the salmon on the grill skin-side down and cook for approximately 5 minutes without moving it to ensure a good sear.
Add the asparagus to the grill and cook for 4-6 minutes, turning occasionally until charred and tender-crisp.
Carefully flip the salmon and cook for an additional 2-3 minutes until the internal temperature reaches 145 degrees Fahrenheit.
Remove from the grill and let the salmon rest for 2 minutes before serving alongside the grilled asparagus.