01 - Preheat oven to 400°F. Line a baking dish with parchment paper or lightly grease it.
02 - Pat fish fillets dry with paper towels and season both sides with salt and black pepper.
03 - Place the fillets in a single layer in the prepared baking dish.
04 - In a small bowl, combine melted butter, lemon juice, lemon zest, minced garlic, chopped parsley, and paprika if using.
05 - Pour the lemon butter mixture evenly over the fish fillets.
06 - Place a lemon slice atop each fillet.
07 - Bake for 15 to 20 minutes, until fish is opaque and flakes easily with a fork.
08 - Remove from oven, garnish with extra parsley, and serve immediately.