Prep the chicken: Pat the chicken dry with paper towels. If using breasts thicker than 1 inch, lightly pound to even thickness for consistent cooking.
Make the Cajun rub: In a small bowl, mix smoked paprika, sweet paprika, cayenne, garlic powder, onion powder, oregano, thyme, black pepper, and salt.
Season: Drizzle 1 tablespoon oil and the lemon juice over the chicken.
Sprinkle the spice blend evenly on both sides, pressing gently so it adheres.
Preheat and sear: Heat a large oven-safe skillet over medium-high heat. Add the remaining 1 tablespoon oil. When the oil shimmers, add the chicken in a single layer.
Sear 3–4 minutes per side until nicely browned.
Finish cooking: Reduce heat to medium-low. Add the butter to the pan and let it melt, spooning some over the chicken. Continue cooking 3–6 minutes, flipping once, until the internal temperature reaches 165°F (74°C).
Alternatively, transfer the skillet to a 375°F (190°C) oven for 6–10 minutes to finish.
Rest: Remove from heat and let the chicken rest 5 minutes to reabsorb juices.
Garnish and serve: Sprinkle with chopped parsley or green onions. Serve with lemon wedges and your favorite low-carb sides.