Between Sep. 22-28 many restaurants (all around France, but also in Lyon) will have a special lower-priced menu to encourage people to discover restaurants that they might not normally try.
For information about the event (in french): http://www.economie.gouv.fr/fete-gastronomie/accueil
You can book online here (you must book ahead): http://www.tousaurestaurant.com/fr