2d look at unity

 Vector3 dir = enemy.position - transform.position;
float angle = Mathf.Atan2(dir.y,dir.x) * Mathf.Rad2Deg;
transform.rotation = Quaternion.AngleAxis(angle, Vector3.forward);

//Look at 2D job using the unity jobs system
struct LookAtJob : IJobParallelForTransform
{
    public NativeArray<Vector2> targetPositions;
    public void Execute(int index, TransformAccess transform)
    {
        Vector2 dir = targetPositions[index] - (Vector2)transform.position;
        float angle = math.degrees(math.atan2(dir.y, dir.x));
        transform.rotation = Quaternion.AngleAxis(angle, Vector3.forward);
    }
}