Can't enable middleware CORS in Laravel 5.1.46

I'm struggling with this issue, i have and API made in Laravel, one of endpoints needs to be accesible to others servers that make a request, i read several forums, here, i and could'nt find a solution.

This the error that throws me in the front:

Access to fetch at 'http://localhost:8000/api/v1/auth/signup' from origin 'http://localhost:3000' has been blocked by CORS policy: Request header field Content-Type is not allowed by Access-Control-Allow-Headers in preflight response.

i tried to implement a cors middleware, this the code:

<?php namespace App\Http\Middleware;

use Closure;

class CORS {

    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {

        header("Access-Control-Allow-Origin: *");

        // ALLOW OPTIONS METHOD
        $headers = [
            'Access-Control-Allow-Methods'=> 'POST, GET, OPTIONS, PUT, DELETE',
            'Access-Control-Allow-Headers'=> 'Content-Type, X-Auth-Token, Origin'
        ];
        if($request->getMethod() == "OPTIONS") {
            // The client-side application can set only headers allowed in Access-Control-Allow-Headers
            return Response::make('OK', 200, $headers);
        }

        $response = $next($request);
        foreach($headers as $key => $value)
            $response->header($key, $value);
        return $response;
    }
}

in kernel.php:

 protected $routeMiddleware = [
        'cors' => \App\Http\Middleware\Cors::class,

in the routes.php:

Route::post('api/v1/auth/signup', 'Api\AuthApiController@signUpUser')->middleware(['cors']);

Why the cors middleware is not doing nothing? From the server side there's no errors.

via Chebli Mohamed