Apex domains cannot have CNAME records.
Question and response
Question
dig comunitel.net. NS
Answer
comunitel.net. 5 NS ns3.comunitel.net.
comunitel.net. 5 NS ns1.comunitel.net.
comunitel.net. 5 NS ns2.comunitel.net.
Authority
The response has no authority records.
Additional
ns1.comunitel.net. 5 A 212.145.4.97
ns2.comunitel.net. 5 A 212.145.4.98
ns3.comunitel.net. 5 A 217.130.24.50
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0