Begin by removing the meat from the rotisserie chicken, shredding approximately 3 to 4 cups of chicken and setting it aside in a bowl.

In a separate bowl, combine ½ cup of mayonnaise, juice of ½ a lemon, and 1 teaspoon of Dijon mustard. Whisk until smooth.

Add the shredded chicken to the dressing and mix in 1 cup of diced celery and ¼ cup of red onion if using. Stir gently to coat.

Check the salad for creaminess; add more mayonnaise if needed for desired consistency.

Transfer the salad to a covered container and chill in the refrigerator for 10-15 minutes to allow flavors to meld.

Taste and adjust seasonings before serving to ensure optimal flavor.