If you don't care about alcohol and table service, I recommend Volle Nolle. Artu is also open for lunch. Unfortunately a lot of the BEST restaurants in the North End aren't open for lunch.
----- Volle Nolle 351 Hanover St, Boston, MA 02113
There are probably thousands of posts here on Chowhound debating the merits of North End Restaurants. A quick search would get you started. However, I still think that bachslunch's comprehensive post is a must read.