Combine the water and cornstarch in a bowl and whisk it until there are no more lumps. whisk in the tomato paste, balsamic, mustard, brown sugar, hot sauce, and cinnamon.
Warm the oil in a large skillet, not a non-stick, over medium high heat. Add the onions and sprinkle with the salt. This helps pull the moisture out. Move them around occasionally with a wooden spoon so they don't burn. Cook until the edges start to brown. Whatever you do, do not let them burn. Add the garlic and cook for another minute.
Add the liquid, stir, and rub the pan with the wooden spoon to scrape up all the flavorful fond, the brown bits on the bottom. Turn the stove to low and simmer with the lid on for 1 hour. Check frequently to make sure it is not burning and the water has not evaporated. Add water if needed. The final result should be thick, not runny, but not pasty. After an hour, taste and adjust salt and other flavors as you wish.
While the onions are simmering, warm the kraut in a pan or for 15 seconds in the microwave, cook the franks, and prepare the buns.
Lovingly place the frank on the bun, squirt on the mustard, add the onions, and then the kraut.
About the onions. Red onions often have an extra layer of tough paper under the outer layer. Make sure you remove it.
About the tomato paste. If you want, you can substitute a 2 tablespoons of ketchup or a sweet tomato based Kansas City style barbecue sauce for the tomato paste.