Step 1: Preheat oven to 400°F (200°C).
Step 2: In a small bowl, combine melted butter, minced garlic, lemon zest, lemon juice, and chopped parsley to make the sauce.
Step 3: Toss asparagus with olive oil, salt, and pepper in a separate bowl.
Step 4: Place each salmon fillet on a large piece of aluminum foil, season with salt and pepper.
Step 5: Arrange asparagus around the salmon on the foil.
Step 6: Drizzle the lemon garlic butter sauce evenly over the salmon and asparagus.
Step 7: Seal the foil packets tightly, leaving a little space for steam.
Step 8: Bake in the preheated oven for 15-20 minutes, or until salmon is cooked through and asparagus is tender.
Step 9: Carefully open the foil packets and serve immediately.