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