Apex domains cannot have CNAME records.
Question and response
Question
dig blackhost.ltd. NS
Answer
blackhost.ltd. 5 NS ns1.black.host.
blackhost.ltd. 5 NS ns2.black.host.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0