Cook noodles Boil in salted water until al dente. Drain and set aside.
Caramelize onions & cabbage Heat fat in a large pan. Sauté onions until soft and lightly golden. Add cabbage, salt, and sugar (if using). Cook over medium heat 15–20 minutes, stirring often, until soft and caramelized.
Combine Add noodles to the pan. Toss well to coat everything evenly.