In a bowl, combine kosher salt, black pepper, smoked paprika, garlic powder, cayenne, and all-purpose flour. Toss the dry shrimp in the spice-flour mix until evenly coated; shake off any excess flour.

Heat pan

Heat a large heavy skillet (cast iron preferred) over medium-high heat until very hot, about 2–3 minutes. Add 2 tablespoons olive oil and swirl to coat.

Sear shrimp

Arrange shrimp in a single layer, tail side up, without crowding (work in two batches if necessary). Sear 1.5–2 minutes undisturbed until the bottom is golden-brown and a crisp crust forms. Flip and cook 30–60 seconds more until opaque and just cooked through (total cook time per shrimp ~2–3 minutes). Remove shrimp to a warmed plate.

Finish with butter

Lower heat to medium. Add 1 tablespoon unsalted butter to the still-hot pan and swirl to melt, scraping up browned bits. Return all shrimp to the pan and toss briefly (20–30 seconds) in the butter to glaze and finish cooking. Remove from heat immediately to avoid overcooking.

Citrus-Herb Finish

Add lemon and herbs

Zest the lemon before juicing. Squeeze 1–2 teaspoons lemon juice over the glazed shrimp in the pan (or on the serving plate). Sprinkle the lemon zest, chopped parsley, and chives evenly over the shrimp. Drizzle 1 teaspoon extra-virgin olive oil on top and toss gently to combine.

Adjust seasoning

Taste one shrimp and adjust seasoning as needed: add a pinch more salt, a grind of black pepper, or a dash of hot sauce for heat.

Serve

Serve the seared Gulf Coast shrimp immediately while hot with crusty bread, warm tortillas, or over mixed greens/slaw. Spoon any buttery pan juices over shrimp and accompaniments. Garnish with an extra sprinkle of chopped parsley and a lemon wedge if desired.