Apex domains cannot have CNAME records.
Question and response
Question
dig campaignengine.io. NS
Answer
campaignengine.io. 3 NS ns9.wixdns.net.
campaignengine.io. 3 NS ns8.wixdns.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0