Apex domains cannot have CNAME records.
Question and response
Question
dig ritail.hk. NS
Answer
ritail.hk. 5 NS louis.ns.cloudflare.com.
ritail.hk. 5 NS elisa.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0