Apex domains cannot have CNAME records.
Question and response
Question
dig netcabo.pt. NS
Answer
netcabo.pt. 1 NS kianchau.ns.cloudflare.com.
netcabo.pt. 1 NS lily.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
lily.ns.cloudflare.com. 2 A 108.162.192.130
lily.ns.cloudflare.com. 2 A 172.64.32.130
lily.ns.cloudflare.com. 2 A 173.245.58.130
kianchau.ns.cloudflare.com. 2 A 108.162.195.179
kianchau.ns.cloudflare.com. 2 A 162.159.44.179
kianchau.ns.cloudflare.com. 2 A 172.64.35.179
lily.ns.cloudflare.com. 2 AAAA 2606:4700:50:0:0:0:adf5:3a82
lily.ns.cloudflare.com. 2 AAAA 2803:f800:50:0:0:0:6ca2:c082
lily.ns.cloudflare.com. 2 AAAA 2a06:98c1:50:0:0:0:ac40:2082
kianchau.ns.cloudflare.com. 2 AAAA 2606:4700:58:0:0:0:a29f:2cb3
kianchau.ns.cloudflare.com. 2 AAAA 2803:f800:50:0:0:0:6ca2:c3b3
kianchau.ns.cloudflare.com. 2 AAAA 2a06:98c1:50:0:0:0:ac40:23b3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0