Apex domains cannot have CNAME records.
Question and response
Question
dig olgdns.eu. NS
Answer
olgdns.eu. 1 NS ns2.lexsynergy.us.
olgdns.eu. 1 NS ns3.lexsynergy.info.
olgdns.eu. 1 NS ns1.lexsynergy.net.
Authority
The response has no authority records.
Additional
ns1.lexsynergy.net. 3 A 194.58.196.54
ns2.lexsynergy.us. 3 A 45.79.129.26
ns3.lexsynergy.info. 3 A 162.13.177.111
ns1.lexsynergy.net. 3 AAAA 2a01:3f1:854:0:0:0:0:53
ns2.lexsynergy.us. 3 AAAA 2600:3c03:e000:958:0:0:0:0
ns3.lexsynergy.info. 3 AAAA 2a00:1a48:7807:103:be76:4eff:fe08:d749
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0