Apex domains cannot have CNAME records.
Question and response
Question
dig pwc.com. NS
Answer
pwc.com. 5 NS pdns2.cscdns.net.
pwc.com. 5 NS pdns1.cscdns.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0