Apex domains cannot have CNAME records.
Question and response
Question
dig biznetgio.pt. NS
Answer
biznetgio.pt. 4 NS ns2.biznetgio.pt.
biznetgio.pt. 4 NS ns1.biznetgio.pt.
Authority
The response has no authority records.
Additional
ns1.biznetgio.pt. 4 A 103.58.102.220
ns2.biznetgio.pt. 4 A 103.93.67.99
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0