Double O’ Burgers specializes in smash-style onion burgers where thin patties are pressed on the griddle with onions, then topped with cheese and sauce on a soft bun.[2][30] The defining element is the onion integration, with the onions cooked directly into the patty surface to create extra caramelization and savoriness.[2][30] When you eat it, you get a mix of crisp beef edges, sweet browned onion, and melted cheese that feels rich yet relatively simple.[2][30] Discussions among local burger fans point to this onion-forward smash style as the reason this Capitol Hill window has developed a following.[2][8][24][30]