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