Apex domains cannot have CNAME records.
Question and response
Question
dig rdsnet.eu. NS
Answer
rdsnet.eu. 5 NS ns.rdsnet.ro.
rdsnet.eu. 5 NS ns.rdsnet.tech.
rdsnet.eu. 5 NS ns.rdsnet.eu.
rdsnet.eu. 5 NS ns.rdsnet.org.
Authority
The response has no authority records.
Additional
ns.rdsnet.eu. 5 A 82.79.10.12
ns.rdsnet.org. 5 A 86.121.222.12
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0