Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Snap the woody ends off the asparagus spears and arrange them in a single layer on one side of the prepared baking sheet.
Place the salmon fillet on the opposite side of the sheet, leaving space for heat to circulate around the fish.
Drizzle the extra virgin olive oil evenly over both the salmon fillet and the asparagus spears.
In a small bowl, combine the dried oregano, garlic powder, sea salt, and black pepper, then sprinkle this seasoning mixture over the salmon and asparagus.
Slice the lemon into thin rounds and layer them directly over the top of the salmon fillet to infuse it with bright citrus notes.
Bake for 12 to 15 minutes, or until the salmon is opaque and flakes easily with a fork and the asparagus is crisp-tender.
Serve immediately, squeezing any remaining lemon juice over the entire dish for a fresh, clean finish.