Apex domains cannot have CNAME records.
Question and response
Question
dig ferret-one.com. NS
Answer
ferret-one.com. 5 NS ns-858.awsdns-43.net.
ferret-one.com. 5 NS ns-1129.awsdns-13.org.
ferret-one.com. 5 NS ns-1805.awsdns-33.co.uk.
ferret-one.com. 5 NS ns-403.awsdns-50.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0