Who cares if that is in Portland (I do not think so) because the best burger I have eaten here was from Slow Bar. The Slow Burger.
For a mere 10 dollars you get 1/2lb. Painted Hills natural beef, Gruyere, onion rings, butter lettuce, pickle relish, garlic aioli. Get it with the salad because the delicious vinaigrette cuts through the richness of the burger. The bar is pretty douchey but damn if that is not the most delicious burg.
I ate a very similar concoction tonight. It's all about squishing that shit until it is almost flat, and then cutting it in half.