Apex domains cannot have CNAME records.
Question and response
Question
dig bigbearnetworks.com. NS
Answer
bigbearnetworks.com. 5 NS ns-712.awsdns-25.net.
bigbearnetworks.com. 5 NS ns-1841.awsdns-38.co.uk.
bigbearnetworks.com. 5 NS ns-1740.awsdns-25.co.uk.
bigbearnetworks.com. 5 NS ns-874.awsdns-45.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0