Preheat oven to 450 ° F.
In a small bowl, melt butter in the microwave. Add thyme leaves and freshly ground pepper to the melted butter and stir. Set aside to allow flavors to meld and butter to cool.
Rinse chicken breasts and pat dry with paper towels. Place chicken breasts, breast side up into roasting pan.
Brush melted butter all over the surface of the chicken. Sprinkle any thyme remaining in the butter dish onto the chicken.
Bake uncovered 45-55 minutes, or until juices run clear and chicken registers 165 ° F. Time will vary based on the size of your chicken breasts.
Remove from oven and allow to rest for 5-7 minutes before serving.