Apex domains cannot have CNAME records.
Question and response
Question
dig linuxnet.cloud. NS
Answer
linuxnet.cloud. 5 NS sarah.ns.cloudflare.com.
linuxnet.cloud. 5 NS david.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0