Apex domains cannot have CNAME records.
Question and response
Question
dig vpls.net. NS
Answer
vpls.net. 5 NS ns2.vpls.net.
vpls.net. 5 NS ns1.iad1.vpls.net.
vpls.net. 5 NS ns1.vpls.net.
Authority
The response has no authority records.
Additional
ns1.iad1.vpls.net. 5 A 74.222.145.145
ns1.vpls.net. 5 A 209.11.240.38
ns2.vpls.net. 5 A 74.222.141.141
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0