Apex domains cannot have CNAME records.
Question and response
Question
dig stg-apse2-trusted.docebomail.com. NS
Answer
stg-apse2-trusted.docebomail.com. 5 NS ns-926.awsdns-51.net.
stg-apse2-trusted.docebomail.com. 5 NS ns-1337.awsdns-39.org.
stg-apse2-trusted.docebomail.com. 5 NS ns-1751.awsdns-26.co.uk.
stg-apse2-trusted.docebomail.com. 5 NS ns-43.awsdns-05.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0