Apex domains cannot have CNAME records.
Question and response
Question
dig spectrum.com. NS
Answer
spectrum.com. 5 NS a12-66.akam.net.
spectrum.com. 5 NS a11-65.akam.net.
spectrum.com. 5 NS a24-64.akam.net.
spectrum.com. 5 NS a1-84.akam.net.
spectrum.com. 5 NS a7-65.akam.net.
spectrum.com. 5 NS a16-67.akam.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0