Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper for easy cleanup.
In a small bowl, whisk together the olive oil, lemon juice, minced garlic, dill, parsley, thyme, salt, and pepper. This is your vibrant marinade.
Place the trimmed asparagus onto one side of the prepared baking sheet. Drizzle with about half of the lemon herb marinade and toss to coat evenly. Spread the asparagus in a single layer.
Pat the salmon fillets dry with a paper towel. Place them on the other side of the baking sheet, skin-side down if applicable. Spoon the remaining marinade generously over the top of each salmon fillet.
Arrange the thin lemon slices over the salmon fillets.
Bake for 12-15 minutes, or until the salmon is cooked through and flakes easily with a fork, and the asparagus is tender-crisp. Cooking time will vary depending on the thickness of your salmon.
Serve immediately, enjoying the fresh flavors and minimal cleanup!