How to add a delay to an object that rotates to face a target ?

I am currently using this script to make an enemy face the player :

 public float speed;
 private Transform player;
 
 void Start()
 {
         player = GameObject.FindWithTag ("Shooter").transform;
 }
 
 
 void Update () 
 {
 float z = Mathf.Atan2 ((player.transform.position.y - transform.position.y), (player.transform.position.x - transform.position.x)) * Mathf.Rad2Deg -90 ;
 transform.eulerAngles = new Vector3 (0, 0, z);
 }

How can I slow down this rotation ? The enemy should take a small amount of time to face the player.