Apex domains cannot have CNAME records.
Question and response
Question
dig twnic.tw. NS
Answer
twnic.tw. 5 NS dns2.twnic.net.tw.
twnic.tw. 5 NS dns1.twnic.net.tw.
Authority
The response has no authority records.
Additional
dns1.twnic.net.tw. 5 A 210.65.47.29
dns2.twnic.net.tw. 5 A 103.235.88.2
dns2.twnic.net.tw. 5 AAAA 2406:da14:7c1:9200:2fd0:8a69:6e58:4b01
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0