Apex domains cannot have CNAME records.
Question and response
Question
dig equifax.ivcert.net. NS
Answer
equifax.ivcert.net. 4 NS ns-1899.awsdns-45.co.uk.
equifax.ivcert.net. 4 NS ns-753.awsdns-30.net.
equifax.ivcert.net. 4 NS ns-270.awsdns-33.com.
equifax.ivcert.net. 4 NS ns-1429.awsdns-50.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0