Apex domains cannot have CNAME records.
Question and response
Question
dig taiwancloud.com.tw. NS
Answer
taiwancloud.com.tw. 4 NS dns2.tfn.net.tw.
taiwancloud.com.tw. 4 NS dns1.tfn.net.tw.
Authority
The response has no authority records.
Additional
dns1.tfn.net.tw. 4 A 211.78.215.137
dns2.tfn.net.tw. 4 A 211.78.215.200
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0