This supremely savory, tender brisket tastes like one my Eastern European grandmother would have made if she had access to an Asian pantry. It has the deep tomato essence and piles of sweet caramelized onions that made hers so tasty, but this recipe layers that flavor with a Chinese five-spice rub, and a distinctively Asian soy-ginger-garlic sauce that clings luxuriously to the meat. Try it with the Asian slaw.
Preheat the oven to 325°f. To make the rub, in a small bowl combine the sugar, onion powder, salt, pepper, Chinese five-spice powder, and cayenne pepper. Rub it all over the brisket and set it aside as you prepare the sauce.
In a medium bowl whisk together 3 tablespoons of water, the tomato paste, rice vinegar, soy sauce, honey, chili-garlic sauce, garlic, ginger, mustard, and sesame oil.
Heat the canola oil on in a large Dutch oven or heavy roasting pan over medium heat. Add the brisket and cook until golden, about 6 minutes per side, turning once. (it is fine, good even, if the meat becomes slightly charred). Transfer the meat to a large plate or board.
Add the onions to the pot and cook, scraping the bottom of pan to incorporate browned bits, until the onions are softened, 7 to 8 minutes. Return the brisket to the pot and add the sauce along with ½ cup water. Cover tightly, transfer to the oven and cook until the meat is tender, 2 ½ to 3 hours.
Transfer the meat to a cutting board and allow to cool for 30 minutes at room temperature, or it may be refrigerated at this stage for up to 4 days.
To continue, cut the meat against the grain into 1/4-inch slices. Return the sliced brisket to the sauce and cook, covered, over medium-low heat until warmed through, 10 to 20 minutes. Add water by the tablespoonful to the sauce to loosen it if necessary.
To refrigerate and reheat
Prior to being sliced, the meat and sauce may be stored separately in airtight containers in the refrigerator for up to 4 days. Follow the "to continue" directions above to serve. Already sliced meat may be stored together with the sauce in an airtight container in the refrigerator. Total refrigeration time for the cooked meat, sliced or unsliced, should not exceed 4 days.
To reheat the sliced meat and sauce, place in a sauce-pan, cover, and cook over medium-low heat until warmed through, 10 to 30 minutes depending on the amount. Alternatively, place in a microwave-safe dish, cover with a spatter guard, and microwave on high for about 1 minute for a single portion.