Apex domains cannot have CNAME records.
Question and response
Question
dig math.byu.edu. NS
Answer
math.byu.edu. 5 NS edns3.byu.edu.
math.byu.edu. 5 NS edns2.byu.edu.
math.byu.edu. 5 NS edns1.byu.edu.
Authority
The response has no authority records.
Additional
edns1.byu.edu. 5 A 128.187.223.235
edns2.byu.edu. 5 A 128.187.223.243
edns3.byu.edu. 5 A 157.201.130.110
edns1.byu.edu. 5 AAAA 2620:10f:3007:fb04:0:0:0:eb
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0