Apex domains cannot have CNAME records.
Question and response
Question
dig camp-infra.adobe.net. NS
Answer
camp-infra.adobe.net. 4 NS ns-1359.awsdns-41.org.
camp-infra.adobe.net. 4 NS ns-439.awsdns-54.com.
camp-infra.adobe.net. 4 NS ns-631.awsdns-14.net.
camp-infra.adobe.net. 4 NS ns-1684.awsdns-18.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0