Apex domains cannot have CNAME records.
Question and response
Question
dig managed-vps.net. NS
Answer
managed-vps.net. 5 NS ns4.managed-vps.net.
managed-vps.net. 5 NS ns3.managed-vps.net.
managed-vps.net. 5 NS ns1.managed-vps.net.
managed-vps.net. 5 NS ns2.managed-vps.net.
Authority
The response has no authority records.
Additional
ns1.managed-vps.net. 5 A 173.237.190.226
ns2.managed-vps.net. 5 A 173.237.190.73
ns3.managed-vps.net. 5 A 78.142.63.190
ns4.managed-vps.net. 5 A 79.124.76.3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0