There are couple ways to eliminate CORS, but one of my favourite is to setup reserve proxy server.
Here simplest way how to do it.
1. Install ARR
http://www.iis.net/learn/extensions/installing-application-request-routing-(arr)
2. Enable Proxy
IIS > Select your server > Aplication Request Routing > Server Proxy Setting > Check Enable Proxy
3. Add Url Rewrite inside your site web.config.
<configuration>
<system.webServer>
<rewrite>
<rules>
<rule name="Reverse Proxy to API" stopProcessing="true">
<match url="^api/(.*)" />
<action type="Rewrite" url="http://some.api/v1/{R:1}" />
</rule>
</rules>
</rewrite>
</system.webServer>
</configuration>
4. Done, now when you request /api in your site, it will automatically forward that to http://come.api/v1/
