Preheat your grill or a cast-iron grill pan over medium-high heat.
In a small bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, chopped parsley, and chopped dill to create the marinade.
Pat the salmon fillet dry with a paper towel and season both sides evenly with the sea salt and black pepper.
Brush the salmon and the trimmed asparagus spears with half of the prepared lemon-herb marinade.
Place the salmon on the grill skin-side down and cook for 4-5 minutes until the skin is crispy and the fish releases easily from the grates.
Add the asparagus to the grill alongside the salmon, turning the spears occasionally for 4-6 minutes until they are charred and crisp-tender.
Carefully flip the salmon and cook for another 2-3 minutes until it reaches your desired level of flaky doneness.
Remove the salmon and asparagus from the heat, drizzle with the remaining marinade, and serve immediately.