Apex domains cannot have CNAME records.
Question and response
Question
dig descartes.com. NS
Answer
descartes.com. 5 NS ns-1455.awsdns-53.org.
descartes.com. 5 NS ns-1703.awsdns-20.co.uk.
descartes.com. 5 NS ns-67.awsdns-08.com.
descartes.com. 5 NS ns-736.awsdns-28.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0