Apex domains cannot have CNAME records.
Question and response
Question
dig tcc.net.tw. NS
Answer
tcc.net.tw. 5 NS dns1.taiwanmobile.com.
tcc.net.tw. 5 NS dns2.taiwanmobile.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0