Apex domains cannot have CNAME records.
Question and response
Question
dig spamrl.com. NS
Answer
spamrl.com. 5 NS ns-1840.awsdns-38.co.uk.
spamrl.com. 5 NS ns-105.awsdns-13.com.
spamrl.com. 5 NS ns-975.awsdns-57.net.
spamrl.com. 5 NS ns-1345.awsdns-40.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0