Apex domains cannot have CNAME records.
Question and response
Question
dig entorno.com. NS
Answer
entorno.com. 5 NS ns2-d.entorno.info.
entorno.com. 5 NS ns1-a.entorno.com.
entorno.com. 5 NS ns1-b.entorno.es.
entorno.com. 5 NS ns2-c.entorno.cat.
Authority
The response has no authority records.
Additional
ns1-a.entorno.com. 5 A 199.167.66.121
ns2-d.entorno.info. 5 A 176.97.158.110
ns1-a.entorno.com. 5 AAAA 2610:1c8:b002:0:0:0:0:121
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0