Apex domains cannot have CNAME records.
Question and response
Question
dig iad1.VPLS.NET. NS
Answer
iad1.VPLS.NET. 5 NS ns1.iad1.VPLS.NET.
iad1.VPLS.NET. 5 NS ns2.VPLS.NET.
iad1.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