Apex domains cannot have CNAME records.
Question and response
Question
dig ipv4.telemach.net. NS
Answer
ipv4.telemach.net. 1 NS ns1.telemach.net.
ipv4.telemach.net. 1 NS ns2.telemach.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0