To begin, gather all your ingredients so that you have them within easy reach. Using a food processor or a large knife and cutting board, finely shred the cabbage. Mince the onion. If you are using a food processor for this job, go ahead and include all the onion juice in the recipe.
Place the shredded cabbage and minced onion in a large bowl. Stir in 1/2 cup granulated sugar, mixing well. Set aside.
Using a small saucepan, combine the apple cider vinegar, vegetable oil, yellow mustard, 2 tablespoons sugar, celery seed, salt and black pepper. Whisk together until incorporated. Heat on medium high and bring to a rolling boil.
Pour the hot vinegar sauce over the cabbage and onion mixture. Stir together until combined.
Cover and refrigerate for 4-8 hours before serving. This cabbage salad will keep in the refrigerator for 2-3 weeks. Serves 8-10 people.