Apex domains cannot have CNAME records.
Question and response
Question
dig byu.com. NS
Answer
byu.com. 5 NS edns1.byu.edu.
byu.com. 5 NS edns2.byu.edu.
byu.com. 5 NS edns3.byu.edu.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0