Apex domains cannot have CNAME records.
Question and response
Question
dig vps1.net. NS
Answer
vps1.net. 5 NS ns2.di.city.
vps1.net. 5 NS ns1.di.city.
Authority
The response has no authority records.
Additional
ns1.di.city. 5 A 188.127.247.246
ns2.di.city. 5 A 178.208.87.11
ns2.di.city. 5 AAAA 2a11:3b80:1:0:2b5:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0