In large skillet, heat oil and butter over medium high heat. Add chicken; cook, turning once, until browned on both sides. Remove chicken from skillet; set aside. Add onion and garlic to skillet; cook and stir until softened, but not browned. Return chicken to skillet. Add tomatoes, broth, olives and capers, if desired. Cover; reduce heat and simmer 20-25 minutes or until chicken is no longer pink in center. Serve with rice, if desired.