Brine the chicken breasts in a bowl of warm water with 1/8 cup kosher salt. Let the breasts sit in the mixture to brine for 30 minutes. Remove the breasts from the brine, rinse, and pat down with paper towels.
Heat oven to 450°F.
Prepare the grape mixture: Mix together grapes, vinegar, and honey. Set aside.
Place the chicken breasts on a foil-lined baking sheet. Drizzle both sides (turning once) evenly with the melted butter or olive oil.
Sprinkle the spices evenly over the chicken on both sides.
Pour the grape mixture over the chicken; top with evenly sprinkled fresh rosemary.
Bake for 20-25 minutes, or until the chicken is cooked through and not pink when you slit it with a knife (165°F).
Let the chicken rest for at least 5-10 minutes. Serve immediately with Best Brown Rice.