Put your oven on broil at 500 F. Slice 8 garlic cloves into strips. Then using a sharp knife start making cuts into the meat on the fat cap side. Start "studding" the beef with the sliced garlic by sliding the strips into the slits. Generously season the beef with the salt and pepper
Place the beef in a roasting pan fat side up. Put it into the oven for 10 minutes. Remove from the oven and flip the meat. Place back into the oven for another 10 minutes. Reduce the oven temperature down to 350 F. Pour 6 cups of beef stock into the pan or enough to come halfway up the sides of the beef. Cover the pan in aluminum foil and place back into the oven. Cook for 1 hour
Peel and roughly chop 3 large onions. Heat 2 tablespoons of olive oil over medium heat Add in the onions and 1 teaspoon each of kosher salt, ground black pepper and Cajun seasoning. Slow cook and caramelize the onions for 20 minutes while stirring occasionally. Remove the onions from the heat and allow to cool slightly
In a large bowl whisk together 1 cup of ketchup, 1 cup of chili sauce, 1 cup of brown sugar, 1 tablespoon of garlic powder and 1 tablespoon of onion powder. Fold the onions into the ketchup mixture
At the 1 hour mark remove the brisket from the oven and uncover. Top it with the onion mixture. Cover the brisket back up with the foil and place it back into the oven. Cook for another 2 - 2 1/2 hours
Remove to a cutting board and allow the meat to rest for at least 10-15 minutes before slicing. After the meat has rested, slice it thinly. Serve the brisket drizzled with the pan juices and onions
