Symfony pasar html a la vista

Controlador:

/**
     * @Route("/tabla/pintar", name="pintar")
     */
    public function pintar() {
        $request = Request::createFromGlobals();
        $ancho = $request->query->get('ancho');
        $alto = $request->query->get('alto');
        $tabla = "<table>";
        for ($i = 0; $i < $alto; $i++) {
            $tabla .= "<tr>";
            for ($j = 0; $j < $ancho; $j++) {
                $tabla .= "<td>" . ($j + $i * $ancho) . "</td>";
            }
            $tabla .= "</tr>";
        }
        $tabla .= "</table>";
        return $this->render('tabla/tabla.html.twig', [
                    'tabla' => $tabla,
        ]);
    }

vista:

{% extends 'base.html.twig' %}

{% block title %}Tabla{% endblock %}
  {% block styles %}
      <style>
          footer{
              background-color: red;
          }
          </style>
  {% endblock %}
{% block body %}
{# esto es un comentario #}
    <h1>Esta es la tabla que ha pedido</h1>
  
    {{tabla | raw}}
    <img src="{{ asset('img/gato.jpg') }}" alt=""/>

{% endblock %}