Apex domains cannot have CNAME records.
Question and response
Question
dig apexportal.net. NS
Answer
apexportal.net. 5 NS ns-151.awsdns-18.com.
apexportal.net. 5 NS ns-1063.awsdns-04.org.
apexportal.net. 5 NS ns-985.awsdns-59.net.
apexportal.net. 5 NS ns-1612.awsdns-09.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0