Apex domains cannot have CNAME records.
Question and response
Question
dig smarthub.coop. NS
Answer
smarthub.coop. 3 NS ns-972.awsdns-57.net.
smarthub.coop. 3 NS ns-1751.awsdns-26.co.uk.
smarthub.coop. 3 NS ns-179.awsdns-22.com.
smarthub.coop. 3 NS ns-1155.awsdns-16.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0