echo $this->Form->input('direccion');
echo $this->Form->input('persona.nombre');
echo $this->Form->input('persona.voluntario.cv');

if ($this->request->is(['patch', 'post', 'put'])) {
    $contact_table = TableRegistry::get('Contacto');
    $contact = $contact_table->patchEntity($contact, $this->request->data, [
        'associated' => ['Persona' => ['Voluntario']]
    ]);
    if ($contact_table->save($contact)) {
        // etc.