Apex domains cannot have CNAME records.
Question and response
Question
dig tw. NS
Answer
tw. 5 NS g.dns.tw.
tw. 5 NS d.dns.tw.
tw. 5 NS e.dns.tw.
tw. 5 NS b.dns.tw.
tw. 5 NS h.dns.tw.
tw. 5 NS c.dns.tw.
tw. 5 NS a.dns.tw.
tw. 5 NS f.dns.tw.
tw. 5 NS anytld.apnic.net.
Authority
The response has no authority records.
Additional
a.dns.tw. 159842 A 203.73.24.25
b.dns.tw. 159842 A 210.201.138.58
c.dns.tw. 172054 A 203.66.87.201
d.dns.tw. 159842 A 60.199.165.186
e.dns.tw. 134984 A 211.20.231.11
f.dns.tw. 159842 A 40.65.125.222
g.dns.tw. 159842 A 34.141.111.176
h.dns.tw. 171829 A 204.61.216.119
a.dns.tw. 159842 AAAA 2001:45b1:0:5:0:0:0:25
b.dns.tw. 159842 AAAA 2404:0:10a0:0:0:0:0:58
c.dns.tw. 172054 AAAA 2001:b020:0:77:0:0:0:1
d.dns.tw. 159842 AAAA 2001:4541:9010:7:0:0:0:186
e.dns.tw. 134984 AAAA 2001:b000:1e0:c000:0:0:0:11
h.dns.tw. 171829 AAAA 2001:500:14:6119:ad:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0