There are sooo many to choose from but our favourite (and regular) at the moment is the Osteria in Cala Millor. It's sort of half way into the shopping precint in Cala Millor and right up a side street. It isn't fancy and the menu is simple but it is the real McCoy and a real relaxed atmosphere. The pasta and bread are all made on the premises by partners Sylvia and Emanuella (chef). They are always on the top 1 or 2 spot on Trip Advisor for good reason. However they don't do pizza.
But Cala Bona has a few places, we only just discovered Fumetto Bistro on the harbour. We had seen it many times but plucked up the courage to try it last time out. Nice place with decent service and the food was very good. Pretty setting too.
But with a couple hundred places to eat and drink in the resorts in the area you will have more fun discovering new favourites.
Enjoy your stay