Apex domains cannot have CNAME records.
Question and response
Question
dig demo-use1.docebomail.com. NS
Answer
demo-use1.docebomail.com. 5 NS ns-810.awsdns-37.net.
demo-use1.docebomail.com. 5 NS ns-293.awsdns-36.com.
demo-use1.docebomail.com. 5 NS ns-1801.awsdns-33.co.uk.
demo-use1.docebomail.com. 5 NS ns-1251.awsdns-28.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0