Preheat your grill or a heavy grill pan over medium-high heat until hot.
Pat the salmon fillet completely dry with a paper towel to ensure a good sear.
In a small mixing bowl, whisk together the olive oil, lemon juice, lemon zest, dill, parsley, sea salt, black pepper, and garlic powder.
Brush half of the herb and lemon mixture over the top and sides of the salmon fillet.
Toss the asparagus spears in the remaining herb mixture until evenly coated.
Place the salmon skin-side down on the grill and cook for 4 to 5 minutes without moving it.
Add the asparagus to the grill and carefully flip the salmon fillet.
Continue grilling for another 3 to 4 minutes until the salmon is opaque and flakes easily, and the asparagus is tender with light char marks.
Remove from the heat and serve immediately while hot.