Apex domains cannot have CNAME records.
Question and response
Question
dig eduroam.uk. NS
Answer
eduroam.uk. 5 NS ns11.ja.net.
eduroam.uk. 5 NS ns12.ja.net.
eduroam.uk. 5 NS ns10.ja.net.
Authority
The response has no authority records.
Additional
ns10.ja.net. 3 A 128.86.8.53
ns11.ja.net. 3 A 195.195.131.244
ns12.ja.net. 3 A 194.83.56.250
ns10.ja.net. 3 AAAA 2001:630:0:42:0:0:0:53
ns11.ja.net. 3 AAAA 2001:630:1:8:0:0:244:0
ns12.ja.net. 3 AAAA 2001:630:1:129:0:0:0:250
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0