In a small bowl, combine the chili powder, salt and pepper; rub over chicken. In a large skillet, saute chicken in butter until golden brown. Reduce heat; cover and cook for 30 minutes or until juices run clear., Transfer chicken to a serving platter and keep warm. Add orange juice to skillet, stirring to loosen browned bits from pan; simmer for 5 minutes. Pour over chicken. Sprinkle with peanuts. Garnish with orange slices and cilantro if desired.