Preheat oven to 375°F (190°C).
Line baking dish with foil or parchment paper.
Place salmon fillets skin-down on the baking dish.
In bowl, mix butter, garlic, lemon juice, zest.
Add parsley, paprika, salt, and pepper. Stir well.
Spoon or brush garlic butter over each fillet.
Add lemon slices on top, if using.
Bake uncovered for 12–15 minutes until flaky.
Broil last 2 minutes for crispy, golden top.
Remove, rest for 2 minutes, serve warm.