Apex domains cannot have CNAME records.
Question and response
Question
dig active-dns.com. NS
Answer
active-dns.com. 4 NS pns6.cloudns.net.
active-dns.com. 4 NS ns4.cloudns.net.
active-dns.com. 4 NS ns1.cloudns.net.
active-dns.com. 4 NS pns4.cloudns.net.
active-dns.com. 4 NS pns3.cloudns.net.
active-dns.com. 4 NS pns8.cloudns.net.
active-dns.com. 4 NS pns2.cloudns.net.
active-dns.com. 4 NS ns3.cloudns.net.
active-dns.com. 4 NS pns9.cloudns.net.
active-dns.com. 4 NS pns1.cloudns.net.
active-dns.com. 4 NS pns5.cloudns.net.
active-dns.com. 4 NS ns2.cloudns.net.
active-dns.com. 4 NS pns7.cloudns.net.
Authority
The response has no authority records.
Additional
ns2.cloudns.net. 4 A 5.161.86.199
pns1.cloudns.net. 4 A 185.136.96.111
pns4.cloudns.net. 4 A 185.136.99.111
ns2.cloudns.net. 4 AAAA 2a01:4ff:f0:94da:0:0:0:1
pns1.cloudns.net. 4 AAAA 2a06:fb00:1:0:0:0:1:111
pns4.cloudns.net. 4 AAAA 2a06:fb00:1:0:0:0:4:111
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0