Heat a large skillet over medium heat for about 1 minute.
In a small bowl, combine the paprika, garlic powder, salt, and black pepper.
Pat the fish fillets dry with paper towels, then rub the seasoning mixture evenly over both sides.
Add the olive oil to the hot skillet. Place the fish in the pan and cook for about 2 minutes per side, or until lightly golden and cooked through.
Transfer the fish to a plate and reduce the heat to low.
Add the butter to the skillet and cook for 1–2 minutes, stirring occasionally, until it begins to turn lightly golden.
Add the lemon juice, minced parsley, and a pinch of salt and pepper. Stir and cook over low heat for about 2 minutes until the sauce is smooth.
Add a few lemon slices to the skillet and return the fish to the pan.
Cook over medium-low heat for about 3 minutes, spooning the lemon butter sauce over the fillets every 30 seconds.
Garnish with fresh parsley and additional lemon slices. Serve immediately with your favorite sides.