Preheat your oven to 400 degrees Fahrenheit (200 degrees Celsius). Line a large baking sheet with parchment paper for easy cleanup.
In a small bowl, mix together the olive oil, minced garlic, oregano, salt, and pepper.
Place the trimmed asparagus on one side of the prepared baking sheet. Drizzle half of the oil mixture over the asparagus and toss to coat evenly. Spread the asparagus into a single layer.
Place the salmon fillets on the other side of the baking sheet. Brush the remaining oil mixture evenly over the tops of the salmon fillets.
Arrange thin slices of lemon on top of each salmon fillet.
Bake for 12 to 15 minutes, or until the salmon is cooked through and flakes easily with a fork, and the asparagus is tender-crisp. Cooking time depends on the thickness of your fillets.
Remove from the oven. Garnish with fresh chopped parsley before serving.
Notes
For thicker salmon fillets, you may need to add 2 to 3 extra minutes to the cooking time.
You can substitute broccoli florets for asparagus if desired; adjust cooking time slightly if needed.
Use fresh lemon juice over the finished dish for extra brightness.