Apex domains cannot have CNAME records.
Question and response
Question
dig com.tw. NS
Answer
com.tw. 5 NS e.twnic.net.tw.
com.tw. 5 NS g.twnic.net.tw.
com.tw. 5 NS c.twnic.net.tw.
com.tw. 5 NS h.twnic.net.tw.
com.tw. 5 NS b.twnic.net.tw.
com.tw. 5 NS anytld.apnic.net.
com.tw. 5 NS a.twnic.net.tw.
com.tw. 5 NS f.twnic.net.tw.
com.tw. 5 NS d.twnic.net.tw.
com.tw. 5 NS h.dns.tw.
Authority
The response has no authority records.
Additional
h.dns.tw. 172704 A 204.61.216.119
h.dns.tw. 172704 AAAA 2001:500:14:6119:ad:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0