Pat the chicken breasts dry with paper towels to remove surface moisture, which helps achieve a crisp sear. Season generously with salt, pepper, and smoked paprika on all sides.
Heat a cast iron skillet over medium-high heat until the oil is shimmering and just begins to smoke slightly. This ensures a hot surface for a perfect sear.
Carefully lay the chicken breasts into the hot skillet, placing them smooth side down. You should hear a satisfying sizzle as they make contact, and the surface should start to turn golden in about 2 minutes.
Let the chicken cook undisturbed for 5-6 minutes until the underside is deep golden brown and releases easily from the pan.
Flip the chicken breasts using tongs, then reduce the heat slightly to prevent burning. Cook for another 5-7 minutes, checking occasionally, until the internal temperature reaches 74°C / 165°F and juices run clear.
Once cooked through, remove the chicken from the skillet and let it rest on a plate for 3-5 minutes; this helps retain juices.
While the chicken rests, add a tablespoon of butter to the skillet and swirl until melted, picking up any flavorful browned bits from the bottom. Squeeze fresh lemon juice over the chicken for brightness.
Slice the rested chicken breasts against the grain and arrange on plates. Drizzle with the buttery pan juices and lemon, then serve immediately.
