Apex domains cannot have CNAME records.
Question and response
Question
dig spamh.com. NS
Answer
spamh.com. 4 NS ns-1841.awsdns-38.co.uk.
spamh.com. 4 NS ns-16.awsdns-02.com.
spamh.com. 4 NS ns-672.awsdns-20.net.
spamh.com. 4 NS ns-1230.awsdns-25.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0