Apex domains cannot have CNAME records.
Question and response
Question
dig dia-static.allophone.net. NS
Answer
dia-static.allophone.net. 5 NS ns-1904.awsdns-46.co.uk.
dia-static.allophone.net. 5 NS ns-932.awsdns-52.net.
dia-static.allophone.net. 5 NS ns-250.awsdns-31.com.
dia-static.allophone.net. 5 NS ns-1275.awsdns-31.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0