Place the shredded cabbage, carrots, and sliced onion in a large mixing bowl, feeling the textures as you gently toss to combine.
In a small bowl, whisk together the mayonnaise, apple cider vinegar, sugar, salt, and black pepper until smooth and creamy, with a tangy aroma.
Pour the dressing over the shredded vegetables, then fold gently with a spatula until every piece is evenly coated and glistening.
Transfer the coleslaw to the refrigerator and let it chill for at least 30 minutes, allowing flavors to meld and the texture to soften slightly while maintaining crunch.
Give the coleslaw a final toss, taste and adjust seasoning if needed, then serve chilled for a crisp, creamy side dish bursting with tangy flavor.