Apex domains cannot have CNAME records.
Question and response
Question
dig by. NS
Answer
by. 5 NS dns3.tld.becloudby.tech.
by. 5 NS dns7.tld.becloudby.com.
by. 5 NS dns2.tld.becloudby.tech.
by. 5 NS dns1.tld.becloudby.com.
by. 5 NS dns4.tld.becloudby.tech.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0