Pat the shrimp dry with paper towels to remove excess moisture.
Heat the cast iron skillet over medium-high heat for 2 minutes until hot.
Add 2 tablespoons of butter to the skillet and let it melt completely.
Add the minced garlic to the skillet and sauté for 30 seconds until fragrant, stirring constantly to avoid burning.
Add the shrimp in a single layer to the skillet. Sprinkle smoked paprika, crushed red pepper flakes, salt, and black pepper evenly over the shrimp.
Cook the shrimp for 2-3 minutes on one side without moving them until they turn pink and start to curl.
Flip the shrimp over and add the remaining 2 tablespoons of butter. Continue cooking for another 2-3 minutes until shrimp are opaque and cooked through.
Remove the skillet from heat and stir in the fresh lemon juice and chopped parsley.
Give everything a quick toss to coat the shrimp in the garlic butter sauce.
Serve immediately, garnished with extra parsley if desired.