Apex domains cannot have CNAME records.
Question and response
Question
dig security. NS
Answer
security. 1 NS a.nic.security.
security. 1 NS e.nic.security.
security. 1 NS b.nic.security.
security. 1 NS f.nic.security.
Authority
The response has no authority records.
Additional
a.nic.security. 23976 A 194.169.218.68
b.nic.security. 23976 A 185.24.64.68
e.nic.security. 23976 A 212.18.248.68
f.nic.security. 23976 A 212.18.249.68
a.nic.security. 23976 AAAA 2001:67c:13cc:0:0:0:1:68
b.nic.security. 23976 AAAA 2a04:2b00:13cc:0:0:0:1:68
e.nic.security. 23976 AAAA 2a04:2b00:13ee:0:0:0:0:68
f.nic.security. 23976 AAAA 2a04:2b00:13ff:0:0:0:0:68
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0