Apex domains cannot have CNAME records.
Question and response
Question
dig lg.co.kr. NS
Answer
lg.co.kr. 5 NS secns.lg.co.kr.
lg.co.kr. 5 NS prmns.lg.co.kr.
Authority
The response has no authority records.
Additional
prmns.lg.co.kr. 5 A 165.243.5.15
secns.lg.co.kr. 5 A 27.122.242.230
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0