Grate the carrots, apples, and onion (optional) with the large side of a box grater and add to the bowl with the vinaigrette.
3 medium carrots, 2 medium apples, 1 small onion
Mix very well. Taste and adjust seasoning if needed. The salad can be served immediately but tastes best after resting for about 30 minutes at room temperature. Store in a sealed container in the refrigerator for up to five days.