Apex domains cannot have CNAME records.
Question and response
Question
dig adobe-campaign.net. NS
Answer
adobe-campaign.net. 5 NS ns-261.awsdns-32.com.
adobe-campaign.net. 5 NS ns-1856.awsdns-40.co.uk.
adobe-campaign.net. 5 NS ns-1527.awsdns-62.org.
adobe-campaign.net. 5 NS ns-653.awsdns-17.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0