Apex domains cannot have CNAME records.
Question and response
Question
dig ja.net. NS
Answer
ja.net. 5 NS ns0.ja.net.
ja.net. 5 NS ns1.surfnet.nl.
ja.net. 5 NS ns1.ja.net.
ja.net. 5 NS ns4.ja.net.
ja.net. 5 NS ns2.ja.net.
Authority
The response has no authority records.
Additional
ns0.ja.net. 5 A 128.86.1.20
ns0.ja.net. 5 A 193.63.94.20
ns1.ja.net. 5 A 194.81.227.226
ns1.surfnet.nl. 5 A 192.87.106.101
ns2.ja.net. 5 A 193.63.105.17
ns4.ja.net. 5 A 193.62.157.66
ns0.ja.net. 5 AAAA 2001:630:0:8:0:0:0:14
ns0.ja.net. 5 AAAA 2001:630:0:9:0:0:0:14
ns1.ja.net. 5 AAAA 2001:630:0:44:0:0:0:e2
ns1.surfnet.nl. 5 AAAA 2001:610:1:800a:192:87:106:101
ns2.ja.net. 5 AAAA 2001:630:0:45:0:0:0:11
ns4.ja.net. 5 AAAA 2001:630:0:47:0:0:0:42
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0