Preheat: First, preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Arrange: Next, place the asparagus on the baking sheet. Drizzle with 1 tbsp olive oil, salt, and pepper. Toss to coat and push to one side.
Place Salmon: Then, place the salmon fillets on the sheet pan. Pat them dry with a paper towel.
Make Sauce: In a small bowl, whisk together the melted butter, remaining 1 tbsp olive oil, lemon juice, garlic, oregano, salt, and pepper.
Season: After that, brush the mixture generously over the salmon fillets. Top each fillet with a lemon slice.
Roast: Finally, bake for 10-15 minutes, until the asparagus is tender and the salmon is cooked through. Garnish with parsley and serve.