Apex domains cannot have CNAME records.
Question and response
Question
dig pccw.com. NS
Answer
pccw.com. 2 NS dns4.pccw.com.
pccw.com. 2 NS dns3.pccw.com.
Authority
The response has no authority records.
Additional
dns3.pccw.com. 2 A 202.164.27.100
dns4.pccw.com. 2 A 203.29.222.100
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0