Apex domains cannot have CNAME records.
Question and response
Question
dig blackhawk-net.com. NS
Answer
blackhawk-net.com. 5 NS ns-1335.awsdns-38.org.
blackhawk-net.com. 5 NS ns-930.awsdns-52.net.
blackhawk-net.com. 5 NS ns-20.awsdns-02.com.
blackhawk-net.com. 5 NS ns-1753.awsdns-27.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0