Preheat your grill or grill pan to medium-high heat.
In a small bowl, whisk together the olive oil, lemon juice, lemon zest, oregano, garlic powder, salt, and pepper to create the marinade.
Pat the salmon fillet dry with a paper towel and brush half of the herb mixture over the flesh side of the fish.
Trim the woody ends off the asparagus and toss the spears with the remaining herb mixture until evenly coated.
Place the salmon on the grill, skin-side down, and cook for about 4 to 5 minutes without moving it to ensure a crisp skin.
Add the asparagus spears to the grill alongside the salmon, turning them occasionally.
Carefully flip the salmon and grill for another 3 to 4 minutes until the internal temperature reaches 145°F and the asparagus is tender with light char marks.
Remove the salmon and asparagus from the heat and let the fish rest for 2 minutes before serving.