Pat the chicken breasts dry with paper towels, then season with salt and pepper. Place the chicken in a large plastic zipper bag and set aside.
In a small bowl, combine lemon juice, olive oil, lemon zest, 1 tablespoon black pepper, garlic powder, thyme and 1/2 teaspoon kosher salt. Whisk well, then add the mixture to the bag with the chicken, massaging to coat.
Refrigerate the chicken for at last 1 hour, up to overnight.
When ready to cook, preheat a grill to 450 degrees Fahrenheit, greasing the grill grate if necessary.
Grill the chicken breasts for 6 to 8 minute per side, until the internal temperature is 165 degrees Fahrenheit and the juices run clear. Allow the chicken to rest on a cutting board for at least 10 minuets prior to serving. Serve with your favorite sides.