Apex domains cannot have CNAME records.
Question and response
Question
dig cdmon.net. NS
Answer
cdmon.net. 5 NS ns3.cdmon.net.
cdmon.net. 5 NS ns5.cdmondns-01.com.
cdmon.net. 5 NS ns1.cdmon.net.
cdmon.net. 5 NS ns2.cdmon.net.
cdmon.net. 5 NS ns4.cdmondns-01.org.
Authority
The response has no authority records.
Additional
ns1.cdmon.net. 5 A 35.189.106.232
ns2.cdmon.net. 5 A 35.195.57.29
ns3.cdmon.net. 5 A 35.157.47.125
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0