Apex domains cannot have CNAME records.
Question and response
Question
dig ihsmarkit.com. NS
Answer
ihsmarkit.com. 1 NS a1-28.akam.net.
ihsmarkit.com. 1 NS a6-64.akam.net.
ihsmarkit.com. 1 NS a9-65.akam.net.
ihsmarkit.com. 1 NS a10-65.akam.net.
ihsmarkit.com. 1 NS a13-66.akam.net.
ihsmarkit.com. 1 NS a14-67.akam.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0