Apex domains cannot have CNAME records.
Question and response
Question
dig archerdigitalsignedmailer.com. NS
Answer
archerdigitalsignedmailer.com. 5 NS ns-1599.awsdns-07.co.uk.
archerdigitalsignedmailer.com. 5 NS ns-1511.awsdns-60.org.
archerdigitalsignedmailer.com. 5 NS ns-205.awsdns-25.com.
archerdigitalsignedmailer.com. 5 NS ns-946.awsdns-54.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0