Apex domains cannot have CNAME records.
Question and response
Question
dig bucuresti.rdsnet.ro. NS
Answer
bucuresti.rdsnet.ro. 5 NS ns.rdsnet.eu.
bucuresti.rdsnet.ro. 5 NS ns.rdsnet.tech.
bucuresti.rdsnet.ro. 5 NS ns.rdsnet.org.
bucuresti.rdsnet.ro. 5 NS ns.rdsnet.ro.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0