It is a long way from Locarno through Ponte Brolla direction “Centovalli” valley…but it is worth the time. Best you do a little walk to the Monte Comino, so you have more space what will follow for your stomach supply.
Al Pentalino is a trouvaille in this pittoresque village. You should definitifely try the carpaccio, polenta…aww…everything is delicious. Open only in summer with a terrace outside.
www.alpentolino.ch/

This very traditional old grotto in Ascona is no real insider tipp anymore. But you just get authentic, frank ticinese food. There is no menu but you will like what you get. Starts with Salami platter and bread, followed by a pasta course, then meat and mostly polenta then another course with local cheese. The desert is accompanied by either Nut Schnapps or a grappa…or two. The boss (minimum 80 years old) decides how much you pay in the end.

http://www.grottobaldoria.ch/