Apex domains cannot have CNAME records.
Question and response
Question
dig g9.pt. NS
Answer
g9.pt. 1 NS dns.nortenet.pt.
g9.pt. 1 NS dns2.interacesso.pt.
g9.pt. 1 NS dns2.nortenet.pt.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0