Combine the celery root, fennel, apple and lemon juice in a large bowl and season with salt and pepper. Toss everything together and set aside for at least 30 minutes and up to 2 hours. This not only tenderizes and marinates the vegetables so they become pliable but also stops them from turning brown.
Combine the mayonnaise, sour cream, vinegar, honey and mustard in a small bowl. Season with salt and pepper.
Pour the dressing over the vegetable and toss well. Fold in the dried cranberries. Taste and season with salt and pepper if needed.
Recipe courtesy of Guy Fieri