Apex domains cannot have CNAME records.
Question and response
Question
dig interlan.nu. NS
Answer
interlan.nu. 5 NS ns.interlan.se.
interlan.nu. 5 NS anycast.interlan.nu.
interlan.nu. 5 NS nsu.interlan.nu.
interlan.nu. 5 NS nsa.interlan.nu.
Authority
The response has no authority records.
Additional
ns.interlan.se. 5 A 192.71.21.37
nsa.interlan.nu. 5 A 194.58.192.46
nsu.interlan.nu. 5 A 185.42.137.98
anycast.interlan.nu. 5 A 194.58.198.32
ns.interlan.se. 5 AAAA 2001:67c:2448:10:0:0:0:151
nsa.interlan.nu. 5 AAAA 2a01:3f1:46:0:0:0:0:53
nsu.interlan.nu. 5 AAAA 2a01:3f0:400:0:0:0:0:32
anycast.interlan.nu. 5 AAAA 2a01:3f1:3032:0:0:0:0:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0