Yeah, another "where to get the best hamburger" thread but this one is different.
Almost all the ones on this site tell you about places that pile on great toppings and the burger is great because of what they put on it. I'm looking for places that have a great burger on a great bun and you can either eat it that way or dress it yourself.
At the moment, my favorite is Cassell's even though it's not as good as it once was. They have good meat (they use a better cut than most burger joints) and the people there really know how to cook it. Unfortunately, the buns are undistinguished, the place is shabby and every so often, you get a bad outlier burger there.
So where can I get a great burger that's just a great burger?