Bouillon has a range of restaurants catering mainly to Belgian and Dutch weekend visitors, so standards are reasonable and portions are generous. Ardennes specialities are the thing to eat: sanglier (wild boar) in season, smoked Ardennes ham, trout from the Semois, and gibier (game) in autumn. The local bière artisanale from the Ardennes breweries is excellent.
Auberge d'Alsace near the castle is a reliable choice for traditional Belgian cooking. The restaurant terrace above the river at Hôtel de la Poste is the best location for lunch in summer. Most restaurants in Bouillon serve similar menus; quality is generally high because the town depends on visitors returning year after year.
Tip: come on a weekday or book ahead for summer weekends, when the town fills with Belgian families.