OneToOneField or ForeignKey ?

If I am creating a series of websites, i.e. a portal, then should site be OneToOneField or ForeignKey ?

class Portal(models.Model):
    site = models.OneToOneField(Site, on_delete=models.CASCADE)    
    email = models.EmailField(max_length=100)
    google_analytics_code = models.CharField(max_length=25)
    created = models.DateTimeField(auto_now_add=True)
    active = models.BooleanField(default=True)

    def __str__(self):

EDIT : This was a dump question - it should always be OneToOneField

I’m not sure that that’s as “clear-cut” as you make it sound.

Having site as an FK means you could have multiple Portal referring to the same site. Since you have an active flag, I could envision a use-case where you have multiple Portal for a site, but only one being active at any one time. (You could use a constraint to ensure that.) It really depends upon what might be different between Portal instances.
(Now, you may have already determined that that’s not the case for you - and that’s great. I just don’t think it’s an “always True” answer.)