Who says it’s hard to manage food allergies in a restaurant? More and more I see vegetarian, vegan and gluten-free options listed on menus. And with a little bit of understanding of how food is prepared (soups and sauces thickened with flour, etc.) or a little bit of courage to ask, it’s no problem at all. An example: this birthday dinner at Gaslight, one of my favorite Boston restaurants. Roasted pear salad with walnuts and goat cheese; Brandt Beef Rossini (shown) with potato puree, spinach, a swirl of foie gras butter and sauce Bordelaise; artisan cheese plate (yes to the pickled carrot slices and watercress, no to the toast and jams). Three delicious courses, no sugar, no flour. Onward.