Cook noodles according to package directions. Meanwhile, in a large skillet, cook beef over medium heat until no longer pink; drain.
Drain mandarin oranges and pineapple, reserving juices. Set fruit aside. In a small bowl, whisk cornstarch and reserved juices until smooth; stir in the lemon juice, soy sauce, garlic powder, salt and nutmeg. Pour over beef.
Bring to a boil; cook and stir for 2 minutes or until thickened. Stir in the cashews, oranges and pineapple. Cook for 2 minutes or until heated through. Drain noodles; top with beef mixture. Sprinkle with coconut.