Apex domains cannot have CNAME records.
Question and response
Question
dig wwwsierraclub.com. NS
Answer
wwwsierraclub.com. 4 NS ns-312.awsdns-39.com.
wwwsierraclub.com. 4 NS ns-1021.awsdns-63.net.
wwwsierraclub.com. 4 NS ns-1309.awsdns-35.org.
wwwsierraclub.com. 4 NS ns-1988.awsdns-56.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0