Apex domains cannot have CNAME records.
Question and response
Question
dig bitrix24.site. NS
Answer
bitrix24.site. 4 NS ns-779.awsdns-33.net.
bitrix24.site. 4 NS ns-1737.awsdns-25.co.uk.
bitrix24.site. 4 NS ns-302.awsdns-37.com.
bitrix24.site. 4 NS ns-1243.awsdns-27.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0