Apex domains cannot have CNAME records.
Question and response
Question
dig ad.ucla.edu. NS
Answer
ad.ucla.edu. 5 NS ad5.ad.ucla.edu.
ad.ucla.edu. 5 NS ad10.ad.ucla.edu.
ad.ucla.edu. 5 NS ns1.dns.ucla.edu.
ad.ucla.edu. 5 NS ad9.ad.ucla.edu.
ad.ucla.edu. 5 NS ad-dc-p02.ad.ucla.edu.
ad.ucla.edu. 5 NS ad4.ad.ucla.edu.
ad.ucla.edu. 5 NS ad-dc-p04.ad.ucla.edu.
ad.ucla.edu. 5 NS ad6.ad.ucla.edu.
ad.ucla.edu. 5 NS ad2.ad.ucla.edu.
ad.ucla.edu. 5 NS ad-dc-p01.ad.ucla.edu.
ad.ucla.edu. 5 NS ad8.ad.ucla.edu.
ad.ucla.edu. 5 NS ad1.ad.ucla.edu.
ad.ucla.edu. 5 NS ns3.dns.ucla.edu.
ad.ucla.edu. 5 NS ad-dc-p11.ad.ucla.edu.
ad.ucla.edu. 5 NS ad3.ad.ucla.edu.
ad.ucla.edu. 5 NS ns4.dns.ucla.edu.
ad.ucla.edu. 5 NS ad-dc-p03.ad.ucla.edu.
ad.ucla.edu. 5 NS ns2.dns.ucla.edu.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0