Apex domains cannot have CNAME records.
Question and response
Question
dig premium-vserver.net. NS
Answer
premium-vserver.net. 5 NS ns4.ip-projects.de.
premium-vserver.net. 5 NS ns3.ip-projects.de.
Authority
The response has no authority records.
Additional
ns3.ip-projects.de. 5 A 62.116.159.4
ns4.ip-projects.de. 5 A 217.160.113.37
ns3.ip-projects.de. 5 AAAA 2001:4178:3:a357:62:116:159:4
ns4.ip-projects.de. 5 AAAA 2001:8d8:580:401:217:160:113:37
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0