Apex domains cannot have CNAME records.
Question and response
Question
dig antispamcloud.COM. NS
Answer
antispamcloud.COM. 2 NS ns-781.awsdns-33.net.
antispamcloud.COM. 2 NS ns-1997.awsdns-57.co.uk.
antispamcloud.COM. 2 NS ns-6.awsdns-00.COM.
antispamcloud.COM. 2 NS ns-1287.awsdns-32.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0