the blog owner multisite

In a multisite, how can I get the ID of the owner of the current blog?

I know how to get the current blogs Id using get_current_blog_id(), so given that ID, how would I fetch the ID of the owner of that blog? (there’s just one owner per blog.)

I use this workaround to get the ID of the owner of the current blog:

$thisblog = $current_blog->blog_id;
$mail = get_blog_option($thisblog, 'admin_email');
$user_from_email = get_user_by('email', $mail);
$user_id = $user_from_email->ID;