1 head red cabbage, cored and sliced as thinly as possible
¾ cup red wine vinegar
5 tablespoons white sugar
2 tablespoons balsamic vinegar
1 tablespoon salt
1 ½ teaspoons onion powder
1 teaspoon seasoned salt (such as LAWRY'S®)
½ teaspoon ground black pepper
½ cup olive oil
Put sliced cabbage into a large sealable plastic bag.
Whisk red wine vinegar, sugar, balsamic vinegar, salt, onion powder, seasoned salt, and black pepper together in a bowl; pour into bag with the cabbage. Massage the bag to ensure cabbage is completely coated with liquid. Squeeze as much air from the bag as possible and seal.
Marinate cabbage in refrigerator, massaging the bag several times a day, until the cabbage is softened and the marinade is deep purple in color, at least 2 days.
Pour olive oil into the bag and mix with the cabbage mixture. Seal bag and refrigerate 1 hour more before serving.