Apex domains cannot have CNAME records.
Question and response
Question
dig sixent.net. NS
Answer
sixent.net. 5 NS ns-46.awsdns-05.com.
sixent.net. 5 NS ns-865.awsdns-44.net.
sixent.net. 5 NS ns-1529.awsdns-63.org.
sixent.net. 5 NS ns-1684.awsdns-18.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0