Apex domains cannot have CNAME records.
Question and response
Question
dig uio.no. NS
Answer
uio.no. 5 NS ns2.uio.no.
uio.no. 5 NS ns1.uio.no.
uio.no. 5 NS nn.uninett.no.
uio.no. 5 NS server.nordu.net.
Authority
The response has no authority records.
Additional
nn.uninett.no. 5 A 158.38.0.181
ns1.uio.no. 5 A 129.240.2.6
ns2.uio.no. 5 A 129.240.2.42
server.nordu.net. 5 A 193.10.252.19
nn.uninett.no. 5 AAAA 2001:700:0:503:0:0:aa:5302
ns1.uio.no. 5 AAAA 2001:700:100:2:0:0:0:6
ns2.uio.no. 5 AAAA 2001:700:100:425:0:0:0:42
server.nordu.net. 5 AAAA 2001:948:4:2:0:0:0:19
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0