Heat oil in Dutch Oven or large saucepan over medium high heat until hot. Add chicken, onions and garlic; cook about five minutes or until chicken is browned and onions are tender. Stir in tomatoes, peanut butter, chili powder, salt and red pepper flakes. Bring to a boil.
Reduce heat; cover and simmer 35 minutes.
Serve over rice; sprinkle with chopped peanuts.