01 - In a small mixing bowl, thoroughly combine smoked paprika, garlic powder, onion powder, dried thyme, dried oregano, cayenne pepper, salt, and black pepper to create the Cajun spice blend. Set aside.
02 - Pat the chicken breasts completely dry using paper towels. Evenly rub both sides of each breast with olive oil, then generously apply the prepared Cajun spice blend to all surfaces, ensuring a thorough coating.
03 - Place a large cast-iron skillet over medium-high heat. Once hot, add the unsalted butter and allow it to melt completely.
04 - Carefully place the seasoned chicken breasts into the hot skillet. Sear for 3 to 4 minutes per side, until a deep, blackened crust forms. Reduce the heat to medium-low, cover the skillet, and continue cooking for an additional 8 to 10 minutes, or until the internal temperature of the chicken reaches 165°F. Remove the chicken from the skillet and allow it to rest for 5 minutes.
05 - While the chicken cooks, rinse the long-grain white rice under cold running water until the water runs clear. In a medium saucepan, bring the chicken broth and salt to a rolling boil. Add the rinsed rice, give it a quick stir, then immediately reduce the heat to low. Cover the saucepan and simmer for 15 minutes, or until all the liquid has been absorbed. Remove from heat and let stand, covered, for 5 minutes, then fluff with a fork.
06 - Slice the rested blackened chicken breasts into desired portions. Arrange a bed of the prepared fluffy white rice on serving plates, then place the sliced chicken on top. Garnish with chopped fresh parsley and lemon wedges, if desired, before serving immediately.