How to force Laravel to return Content-Type JSON?

Question

Laravel

How to force laravel to set Content-Type header "application/json; charset=UTF-8"? I also do it through middleware:

public function handle($request, Closure $next) {
  $request->headers->set('Content-Type', 'application/json; charset=UTF-8');
  return $next($request);
}

(I hook to route via "->middleware('json')"), and via the controller:

return response()->json($result)->header('Content-Type', 'application/json; charset=UTF-8');

Anyway, in the browser the header is "content-type: text/html", and the response is not perceived as json.