Apex domains cannot have CNAME records.
Question and response
Question
dig comodo.com. NS
Answer
comodo.com. 5 NS ns2.nurd.com.
comodo.com. 5 NS ns1.nurd.com.
Authority
The response has no authority records.
Additional
ns1.nurd.com. 5 A 199.167.64.4
ns2.nurd.com. 5 A 104.37.177.4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0