Topic: Submit form to central rails application from remote HTML sites

I'd like to submit forms from few remote sites under various domains to the central rails application. Remote sites are pure HTML (I mean no scripting at server side - just JS/jQuery at client side). I know that extremely plain way to do it would be to embed the form within iframe but I'd like to avoid it.

What would be the best and safe pattern to create such interaction?

So far I tried to write simple HTML form addressed to create action inside controller and submit form with AJAX using jQuery. In general it works, however I got "Can't verify CSRF token authenticity" warning so I guess it may be not acceptable in production.

Could someone experienced give me some advice? Thank You.