Cook and stir chicken, onion and red pepper flakes in a skillet over high heat until chicken is lightly browned and onion is tender. Stir in soup, tomatoes, milk and chili powder. Bring to a boil. Reduce heat; cover and simmer 5 minutes. Stir in peanut butter heat through. Meanwhile, bring water to a boil in a saucepan. Stir in rice. Cover; remove from heat. Let stand 5 minutes. Fluff with a fork. Serve chicken over rice.