Apex domains cannot have CNAME records.
Question and response
Question
dig dft.tw. NS
Answer
dft.tw. 5 NS nsa2.dft.tw.
dft.tw. 5 NS nsa1.dft.tw.
Authority
The response has no authority records.
Additional
nsa1.dft.tw. 5 A 116.50.32.207
nsa2.dft.tw. 5 A 103.94.31.50
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0