In a mixing bowl, whisk together 3 tablespoons fresh lemon juice, 1 tablespoon lemon zest, 4 minced garlic cloves, 1 tablespoon olive oil, 1 teaspoon dried thyme (or Italian seasoning), 1 teaspoon salt, ½ teaspoon black pepper, and ¼ teaspoon red pepper flakes if using. Mix thoroughly until all ingredients are well combined and the marinade is emulsified.

Add the pounded chicken breasts to the bowl, ensuring each piece is completely coated with the lemon-garlic marinade. Turn the chicken several times to distribute the flavors evenly. Let the chicken marinate at room temperature for 30-45 minutes. Avoid refrigerating during this time, as room temperature allows for better flavor absorption and more even cooking.

Remove the chicken breasts from the marinade and use paper towels to pat them completely dry on all sides. This critical step removes excess moisture, which is essential for achieving that beautiful golden-brown restaurant-quality sear. Reserve the leftover marinade for the sauce.

Heat the remaining 1 tablespoon of olive oil in a large, heavy skillet (cast iron works exceptionally well) over medium-high heat until it shimmers. Carefully place the dried chicken breasts in the hot pan without overcrowding. Sear for 5-6 minutes on the first side without moving them, allowing a golden crust to develop. Flip and cook for another 5-6 minutes until the internal temperature reaches 165°F (74°C) on an instant-read thermometer.

Transfer the cooked chicken to a clean plate and tent with foil to keep warm. Reduce the heat to medium. Add 1 tablespoon of butter to the same skillet, allowing it to melt and capture all the flavorful browned bits. Pour in the reserved marinade and 2 tablespoons of chicken broth if using. Cook for about 2 minutes, stirring constantly and scraping the bottom of the pan to deglaze, until the sauce reduces slightly and thickens.

Return the seared chicken breasts to the pan with the lemon-garlic sauce. Spoon the sauce generously over each piece, allowing the chicken to absorb the bright flavors for 1-2 minutes. Transfer to serving plates, drizzle with the remaining pan sauce, and garnish with fresh lemon slices and chopped parsley or chives for a pop of color and freshness.