transform.LookAt(target); in 2D?

I think this is the best one.. insert the tag of the object that u want to look at and play with the offset

  public string Tag;
     public float offset;
         
             private Transform target;
             private Vector3 targetPos;
             private Vector3 thisPos;
             private float angle;
         
          void Start () 
                {
                 target = GameObject.FindGameObjectWithTag(Tag).GetComponent<Transform>();
             }
         
          void LateUpdate()
             {
                 targetPos = target.position;
                 thisPos = transform.position;
                 targetPos.x = targetPos.x - thisPos.x;
                 targetPos.y = targetPos.y - thisPos.y;
                 angle = Mathf.Atan2(targetPos.y, targetPos.x) * Mathf.Rad2Deg;
                 transform.rotation = Quaternion.Euler(new Vector3(0, 0, angle + offset));
             }

You can flatten your lookat position in the appropriate axis:

 Vector3 targetPos = target.transform.position;
 Vector3 targetPosFlattened = new Vector3(targetPos.x, targetPos.y, 0);
 transform.LookAt(targetPosFlattened);

There's an amazingly simple solution in this thread (NOT the one marked as 'best' but the one below with the many votes!)

first you have to take the direction to target gameobject then use Quaternion.FromToRotation(Vector3.up, direction) : the first parameter is the current gameobject's up direction and second parameter is the direction to the target gameobject.

  public Transform target;
 
     private void Update()
     {
         Vector2 direction = target.position - transform.position;
         transform.rotation = Quaternion.FromToRotation(Vector3.up, direction);
     }