Pizza

You could get a Margherita (ask for no cheese) at Ken's Artisan Pizza (http://www.kensartisan.com/pizza.html);
Search Yelp: http://www.yelp.com/search?cflt=italian&find_loc=Portland%2C+OR;
Try Nostrana: http://www.nostrana.com/menu.html;
Try Bar Due in the Pearl: http://www.pfmenus.com/?p=115 (ask for no cheese on the margherita);
You could post the question at http://www.portlandfoodanddrink.com

The key to good pizza is San Marzano tomatoes, dough with very little yeast that has been allowed to rise slowly for at least 24 hours, and a 700 - 900 degree F oven.

Personally, if I were vegan, I'd go to Ken's. But the best pizza in town for a non-vegan is Apizza Scholl's. You might ask for the onions and peppers pizza without cheese. I'm sure they do get vegan requests.

That said, there don't seem to be that many places in Portland actually trying to do real Italian pizza. Nostrana is the closest in intent, though I haven't been that impressed.

Edit: And when I say real Italian pizza, I mean a place like this:
A16 in San Francisco, which "Transports the cuisine of Campania and the wood fire of Naples to San Francisco's Marina neighborhood." I even accidentally ordered the vegan pizza and didn't regret it. :)