Apex domains cannot have CNAME records.
Question and response
Question
dig libware.pt. NS
Answer
libware.pt. 5 NS ns3.no-ip.com.
libware.pt. 5 NS ns5.no-ip.com.
libware.pt. 5 NS ns2.no-ip.com.
libware.pt. 5 NS ns1.no-ip.com.
libware.pt. 5 NS ns4.no-ip.com.
Authority
The response has no authority records.
Additional
ns1.no-ip.com. 5 A 194.62.181.53
ns2.no-ip.com. 5 A 194.62.180.53
ns3.no-ip.com. 5 A 204.16.255.53
ns4.no-ip.com. 5 A 204.16.254.53
ns1.no-ip.com. 5 AAAA 2a07:dc00:1810:0:0:0:0:53
ns2.no-ip.com. 5 AAAA 2a07:dc00:180:0:0:0:0:53
ns3.no-ip.com. 5 AAAA 2a07:dc00:2550:0:0:0:0:53
ns4.no-ip.com. 5 AAAA 2620:0:2e64:0:0:0:0:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0