Apex domains cannot have CNAME records.
Question and response
Question
dig arlomail.net. NS
Answer
arlomail.net. 5 NS ns-1369.awsdns-43.org.
arlomail.net. 5 NS ns-216.awsdns-27.com.
arlomail.net. 5 NS ns-830.awsdns-39.net.
arlomail.net. 5 NS ns-1830.awsdns-36.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0