Apex domains cannot have CNAME records.
Question and response
Question
dig cafe24.co.kr. NS
Answer
cafe24.co.kr. 4 NS ns2.cafe24.com.
cafe24.co.kr. 4 NS dns1.cafe24.co.kr.
cafe24.co.kr. 4 NS dns2.cafe24.co.kr.
cafe24.co.kr. 4 NS ns.cafe24.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0