Sprinkle both sides of the brisket evenly with the garlic powder, paprika, mustard, salt and pepper. Heat the canola oil in a large pot over medium-high heat. Add the brisket and cook until browned, about 7 minutes per side. Place the onions underneath the brisket and cook until the onions begin to brown slightly, about 10 minutes. Add the carrots, celery, tomato sauce and enough cold water to cover the brisket by 1 inch. Bring to a boil. Reduce the heat to a simmer, cover and cook until the brisket is tender, about 2 1/2 hours.
Transfer the brisket to a cutting board and thinly slice it against the grain. Return the brisket to the pot and add the potatoes. Add more water if needed for the potatoes to cook. Cook, uncovered, until the potatoes are tender and the sauce is slightly thickened about 30 minutes. Serve immediately.
A viewer or guest of the show, who may not be a professional cook, provided this recipe. It has not been tested for home use.