Apex domains cannot have CNAME records.
Question and response
Question
dig int. NS
Answer
int. 4 NS y.iana-servers.net.
int. 4 NS z.iana-servers.net.
int. 4 NS sec2.authdns.ripe.net.
int. 4 NS ns0.ja.net.
int. 4 NS x.iana-servers.net.
int. 4 NS ns.uu.net.
Authority
The response has no authority records.
Additional
ns0.ja.net. 4 A 128.86.1.20
ns0.ja.net. 4 A 193.63.94.20
ns0.ja.net. 4 AAAA 2001:630:0:8:0:0:0:14
ns0.ja.net. 4 AAAA 2001:630:0:9:0:0:0:14
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0