Apex domains cannot have CNAME records.
Question and response
Question
dig vps.net. NS
Answer
vps.net. 5 NS dns1.vps.net.
vps.net. 5 NS dns2.vps.net.
Authority
The response has no authority records.
Additional
dns1.vps.net. 5 A 67.228.254.4
dns2.vps.net. 5 A 67.228.255.5
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0