Bring to boil, the cider vinegar, oil, sugar, salt & garlic powder, stirring.

Pour the hot dressing over the 2 lbs of cabbage mixture and onions and stir (It will look like there is not enough dressing for the amount of cabbage, but as the cabbage breaks down, you will have plenty).

Cover tightly.

Let sit on the counter for 2 hours (stirring occasionally during the 2 hours while it marinates), then refrigerate.