Riverwalk Cafe in Bricktown, OKC - not on the "river", but on a side street, inside behind Uncommon Grounds but in the same building. I stumbled upon it by accident last week and my office went there for lunch just now, also by accident since our destination was closed thank God.
The hamburger patty was thick and tender and flavorful and smoky and juicy and the outside was crunchy and charred black around the edges. The bun was good solid bread in itself, toasted and buttered and kind of smoky too. Probably the best burger I've had in years. The meat was so good I didn't put anything else on it besides the melted swiss that was already there.
It was so good the office-mates got all competitive about who'd ordered the best thing. The steak sandwich was chunks of sirloin marinated in a teriaki sauce then grilled. (We ended up sharing everything)The cottage fries were very crisp on the ouside and un-greasey and fluffy potato on the inside.
We were the only people there at lunch, but they say they're busy at night. In fact they told us that several times, like "we have good business, really we do". (Of course the Spagetti Warehouse next door was packed.)
As for the collection of clown paintings, well, I managed to nab the chair facing away from them.