Apex domains cannot have CNAME records.
Question and response
Question
dig altibox.net. NS
Answer
altibox.net. 5 NS ns3.altibox.net.
altibox.net. 5 NS ns2.altibox.net.
altibox.net. 5 NS ns1.altibox.net.
Authority
The response has no authority records.
Additional
ns1.altibox.net. 5 A 81.167.36.4
ns2.altibox.net. 5 A 81.167.36.13
ns3.altibox.net. 5 A 45.14.53.4
ns1.altibox.net. 5 AAAA 2a01:798:0:8010:81:167:36:4
ns2.altibox.net. 5 AAAA 2a01:798:0:901a:81:167:36:13
ns3.altibox.net. 5 AAAA 2a01:798:d1:53:0:0:0:4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0