Apex domains cannot have CNAME records.
Question and response
Question
dig acrobat.ai. NS
Answer
acrobat.ai. 5 NS ns206.adobe.net.
acrobat.ai. 5 NS ns201.adobe.net.
acrobat.ai. 5 NS ns204.adobe.net.
acrobat.ai. 5 NS ns202.adobe.net.
acrobat.ai. 5 NS ns203.adobe.net.
acrobat.ai. 5 NS ns205.adobe.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0