Apex domains cannot have CNAME records.
Question and response
Question
dig spectrum.net. NS
Answer
spectrum.net. 5 NS ns-960.awsdns-56.net.
spectrum.net. 5 NS ns-151.awsdns-18.com.
spectrum.net. 5 NS ns-1572.awsdns-04.co.uk.
spectrum.net. 5 NS ns-1336.awsdns-39.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0