Apex domains cannot have CNAME records.
Question and response
Question
dig spf.avature.net. NS
Answer
spf.avature.net. 5 NS ns-454.awsdns-56.com.
spf.avature.net. 5 NS ns-1453.awsdns-53.org.
spf.avature.net. 5 NS ns-855.awsdns-42.net.
spf.avature.net. 5 NS ns-1699.awsdns-20.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0