Apex domains cannot have CNAME records.
Question and response
Question
dig eurodns.eu. NS
Answer
eurodns.eu. 5 NS ns-c.eurodns.eu.
eurodns.eu. 5 NS ns-a.eurodns.com.
eurodns.eu. 5 NS ns-b.eurodns.org.
eurodns.eu. 5 NS ns-d.eurodns.biz.
Authority
The response has no authority records.
Additional
ns-c.eurodns.eu. 5 A 192.174.68.110
ns-d.eurodns.biz. 5 A 176.97.158.110
ns-c.eurodns.eu. 5 AAAA 2001:67c:1bc:0:0:0:0:110
ns-d.eurodns.biz. 5 AAAA 2001:67c:10b8:0:0:0:0:110
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0