Adam Fleischman invented the Umami burger in 2009 after figuring out that one of the main tastes that diners love in burgers and pizza is umami, the fifth taste popular in Japanese cuisine. In order to play up that flavor in the Umami Burger, toppings like an aged Parmesan crisp, oven-roasted tomatoes, shiitake mushrooms (naturally high in umami), and caramelized onions accentuate the taste, while a Portuguese bun holds it all together while adding texture.
The burger patty is seasoned with Fleischman's Umami "Master" Sauce, which includes seaweed, tamari, and miso, and his Umami "Dust," a secret mixture that includes konbu and dried mushrooms, as well as some salt and pepper. To bring it altogether, Umami ketchup kicks up the flavor with added fish sauce and mushrooms. The combination of all of the ingredients creates a hint of Japanese cuisine that’s thrown into a classical American burger.
Purée the tomatoes in a blender, and set aside. Heat the oil in a 4-quart saucepan over medium heat. Add onions; cook until soft, about 8 minutes. Add tomato purée, vinegar, brown sugar, tomato paste, and salt; cook, stirring occasionally, until thick, about 1 hour.
Purée cooked tomato mixture in a blender with the tamari, Worcestershire, and anchovies. Transfer to a bowl; season with salt if needed. Cover and chill before using.