Response to preflight request doesn't pass access control check Laravel and Ajax call

I have a REST api made in Laravel 5.1 hosted in a remote server. Now, I', trying to consume that API from another website (that I have in local).

In Laravel I set the required lines to send the CORS headers. I also tested the API using Postman and everything seems to be ok!

In the Frontend

Then, in the website I sent the POST request using ajax, with this code:

var url="http://ift.tt/2mUN9Py";
var data=$("#my-form").serialize();
    $.ajax({
                    type: "POST",
                    url: url,
                    data: data,
                    headers: { 'token': 'someAPItoken that I need to send'},
                    success: function(data) {
                        console.log(data);
                    },
                    dataType: "json",
                }); 

Buy then I get this error in the console:

XMLHttpRequest cannot load http://ift.tt/2mUN9Py. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost' is therefore not allowed access.

In the Backend

In the API I set this (using a Laravel Middleware to set the headers):

return $next($request)
            ->header('Access-Control-Allow-Origin', '*')
            ->header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');

So, I'm confused about where is exactly the problem.

1. In the server? but then why with Postman work fine?
2. Is in the Ajax call? so, then what should I add?

via Chebli Mohamed