Fetch() not reading response

I have created a Laravel API. Using Fetch() I am trying to submit shopify form data (custom form) on the server. Data is correctly submitting in database. API returns ID of the last inserted row as a response. When I console the response, I am getting null in the body. Here is the screenshot:

Here is the actual response from the API.

You can see that the API returns a number but fetch function is not reading that response.

Here is my code:

    var myHeaders = new Headers();
    myHeaders.append("Content-Type", "application/json");
    myHeaders.append("Access-Control-Allow-Origin", "*");
    var requestOptions = {
        method: 'POST',
        headers: myHeaders,
        mode: 'no-cors',
        body: $("#form").serialize(),
    };
    var cartContents = fetch("https://www.somesite.com/api/quotes", requestOptions)
    .then(function (text) {
        console.log('res',text);
    })
    .catch((error) => {
        throw error;
    });

Here is the laravel API function:

public function store(Request $request)
{
    parse_str($request->getContent(), $data);
          
    $newUser = new User([
        'fname' => $data['fname'],
        'lname' => $data['lname'],
        'email' => $data['email'],
    ]);

    $newUser->save();
    echo $newUser->id;
    die();
}

Here is the code of routes/api.php

    use IlluminateHttpRequest;
    use IlluminateSupportFacadesRoute;
    use AppHttpControllersUser;
    /*
    |--------------------------------------------------------------------------
    | API Routes
    |--------------------------------------------------------------------------
    |
    | Here is where you can register API routes for your application. These
    | routes are loaded by the RouteServiceProvider within a group which
    | is assigned the "api" middleware group. Enjoy building your API!
    |
    */
    Route::post('quotes', [User::class, 'store']);

I don’t understand why it have such a weird behaviour. Can anyone suggest me what I am doing wrong.

Many Thanks!