Apex domains cannot have CNAME records.
Question and response
Question
dig interacesso.pt. NS
Answer
interacesso.pt. 5 NS dns2.nortenet.pt.
interacesso.pt. 5 NS dns.nortenet.pt.
interacesso.pt. 5 NS dns2.interacesso.pt.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0