Apex domains cannot have CNAME records.
Question and response
Question
dig cdns.net. NS
Answer
cdns.net. 5 NS dns7.cdns.net.
cdns.net. 5 NS dns6.cdns.net.
cdns.net. 5 NS dns3.cdns.net.
cdns.net. 5 NS dns1.cdns.net.
cdns.net. 5 NS dns2.cdns.net.
cdns.net. 5 NS dns01.cdns.net.
Authority
The response has no authority records.
Additional
dns1.cdns.net. 5 A 194.0.1.11
dns2.cdns.net. 5 A 194.0.2.11
dns3.cdns.net. 5 A 91.208.95.132
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0