Kosher or coarse salt and freshly ground black pepperto taste
Fresh thyme sprigsto taste
Trim the chicken breasts and use a large sharp knife to cut them into three pieces, about two inches wide each. Cut each of the pieces in half horizontally, so that you have two thinner, small cutlets from each piece. Cut the bell peppers into 2-inch pieces, and discard the stem and any seeds.
In a large container or zipper top bag, combine the lemon juice, olive oil, shallots, thyme, black olives, Sriracha and salt and pepper.
Add the chicken and peppers to the marinade, making sure the marinade coats all of the ingredients. Cover and marinate for 6 to 12 hours, in the refrigerator.
Bring the chicken and peppers to room temperature while you heat the grill to medium high. Grill the chicken and the peppers for 4 or 5 minutes on each side, until nicely browned and cooked through.
Serve the chicken and peppers hot or at room temperature, with the thyme sprigs tucked in.