How to Dig Nameservers of a Domain
With dig Command (Domain Information Groper) we can Retrieve All Types of DNS Record and Can be used to find out NameServers for Domain. To find nameservers for a domain use dig with NS Option.
dig NS google.com
Use +trace option to Search DNS Record starting from the root name servers.
dig NS google.com +trace
Using +trace Option Always Gives the Most Accurate Result.
Nslookup in Windows
If You are Windows Administrator, You can use nslookup as an Alternative to Dig Command, which is pretty much a Unix Command.
nslookup -type=ns linuxcommands.info
-type=ns use retrieve Nameservers With nslookup Command.
nslookup Command Also Available In Linux Operating Systems. So if you are a Linux Administrator Your Job can be easy.