Apex domains cannot have CNAME records.
Question and response
Question
dig spamexperts.net. NS
Answer
spamexperts.net. 5 NS ns-619.awsdns-13.net.
spamexperts.net. 5 NS ns-384.awsdns-48.com.
spamexperts.net. 5 NS ns-1997.awsdns-57.co.uk.
spamexperts.net. 5 NS ns-1071.awsdns-05.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0