Apex domains cannot have CNAME records.
Question and response
Question
dig lu.se. NS
Answer
lu.se. 5 NS nsc.lu.se.
lu.se. 5 NS nsa.lu.se.
lu.se. 5 NS sunic.sunet.se.
Authority
The response has no authority records.
Additional
nsa.lu.se. 5 A 130.235.63.235
nsc.lu.se. 5 A 130.235.10.166
sunic.sunet.se. 5 A 192.36.125.2
nsa.lu.se. 5 AAAA 2001:6b0:16:461:0:0:0:235
nsc.lu.se. 5 AAAA 2001:6b0:16:151:0:0:0:166
sunic.sunet.se. 5 AAAA 2001:6b0:7:0:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0