Preheat the oven to 400°F (200°C).
Line a large sheet pan with parchment paper or lightly grease it with olive oil.
In a large bowl, toss the broccoli florets with 1 tablespoon of olive oil, garlic powder, smoked paprika, salt, and black pepper until evenly coated.
Spread the seasoned broccoli in a single layer on one side of the prepared sheet pan.
Place the salmon fillets on the other side of the sheet pan skin-side down.
Drizzle the remaining 1 tablespoon of olive oil evenly over the salmon fillets.
Place lemon slices on top of each salmon fillet.
Bake in the preheated oven for 18 to 20 minutes, or until the salmon is cooked through and flakes easily with a fork, and the broccoli is tender and slightly browned.
Remove the sheet pan from the oven and sprinkle chopped fresh parsley over the salmon and broccoli.
Serve immediately, optionally squeezing additional lemon juice over the salmon.