Pat the fish fillets dry with paper towels. If fillets are thicker than 1 inch, halve them horizontally or use a gentle butter knife to butterfly so they cook evenly. Season both sides with kosher salt (about 1/2 tsp total distributed) and set on a plate for 5 minutes to let the salt penetrate.

Make pepper rub

In a small bowl combine freshly ground black pepper (2 tbs), garlic powder (1 tsp), and smoked paprika (1 tsp). Mix thoroughly. Spread the all-purpose flour on a plate and press each fillet lightly into the flour to coat both sides thinly; shake off excess flour. Then press each floured fillet into the pepper rub so the pepper mixture adheres evenly, concentrating slightly on the skinless side to create a peppery crust.

Sear the fish

Heat a large skillet over medium-high heat until hot (about 2 minutes). Add 2 tablespoons olive oil and swirl to coat. When oil shimmers, place fillets peppered-side down in the pan without crowding (work in two batches if needed). Cook undisturbed 2 to 3 minutes until a deep golden crust forms on the peppered side. Gently flip using a fish spatula and add 1 tablespoon unsalted butter to the pan. Tilt the pan and spoon the melted butter and oil over the top of the fillets while they finish cooking 1 to 3 minutes more, until the fish registers 130–135°F (54–57°C) for moist, flaky fish or until opaque and flakes easily with a fork.

Finish and serve

Remove fillets to a warm plate. Immediately squeeze 1 tablespoon fresh lemon juice over the cooked fish and sprinkle with 2 tablespoons chopped fresh parsley. Serve with lemon wedges on the side for additional acidity. Taste and add more cracked pepper or salt if desired.

Notes

If using very thin fillets (tilapia, sole), reduce initial sear time to 1–1.5 minutes and finish 30–60 seconds after flipping. For extra heat, add 1/2 teaspoon crushed red pepper to the rub. Ensure oil is hot before adding fish to prevent sticking and promote crust formation.