Preheat your oven to 400°F (200°C). Line a large, rimmed sheet pan with parchment paper for super easy cleanup. This prevents sticking and makes washing a breeze!

In a small bowl, whisk together 2 tablespoons of olive oil, the juice from one lemon, minced garlic, dried dill (or oregano), salt, black pepper, and the optional red pepper flakes. This is your zesty, aromatic flavor base for everything.

On one side of your prepared sheet pan, spread out the trimmed asparagus spears in a single layer. Drizzle them with the remaining 1 tablespoon of olive oil and half of the lemon-herb mixture. Toss gently with your hands or tongs to ensure they're all coated.

Place the salmon fillets skin-side down (if they have skin) on the other side of the sheet pan, leaving a little space between each fillet and the asparagus. Brush the remaining lemon-herb mixture generously over the top of each salmon fillet.

Artfully arrange the thin slices of the second lemon over and around the salmon and asparagus. As they bake, these slices will infuse even more bright, fresh flavor into the dish.

Transfer the sheet pan to the preheated oven and bake for 12-18 minutes. The salmon is done when it's opaque throughout and flakes easily with a fork, and the asparagus should be crisp-tender and slightly charred in spots. Cooking time will depend on the thickness of your salmon fillets.

Carefully remove the sheet pan from the oven. Garnish generously with fresh chopped parsley or dill before serving immediately. This meal is fantastic on its own or with a simple side of quinoa or rice!