Apex domains cannot have CNAME records.
Question and response
Question
dig viatel.net. NS
Answer
viatel.net. 5 NS ns1-auth.viatel.net.
viatel.net. 5 NS ns3-auth.viatel.net.
viatel.net. 5 NS ns2-auth.viatel.net.
Authority
The response has no authority records.
Additional
ns1-auth.viatel.net. 5 A 83.147.159.0
ns2-auth.viatel.net. 5 A 83.147.159.1
ns3-auth.viatel.net. 5 A 83.147.159.2
ns1-auth.viatel.net. 5 AAAA 2a01:258:0:0:0:0:100:0
ns2-auth.viatel.net. 5 AAAA 2a01:258:0:0:0:0:100:1
ns3-auth.viatel.net. 5 AAAA 2a01:258:0:0:0:0:100:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0