Apex domains cannot have CNAME records.
Question and response
Question
dig ist.berkeley.edu. NS
Answer
ist.berkeley.edu. 4 NS adns3.berkeley.edu.
ist.berkeley.edu. 4 NS adns2.berkeley.edu.
ist.berkeley.edu. 4 NS adns1.berkeley.edu.
Authority
The response has no authority records.
Additional
adns1.berkeley.edu. 1 AAAA 2607:f140:ffff:fffe:0:0:0:3
adns2.berkeley.edu. 1 AAAA 2607:f140:ffff:fffe:0:0:0:e
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0