Apex domains cannot have CNAME records.
Question and response
Question
dig retail.datagroup.ua. NS
Answer
retail.datagroup.ua. 5 NS ns1.retail.datagroup.ua.
retail.datagroup.ua. 5 NS ns2.newline.net.ua.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0