Day before cooking, season the brisket with salt and pepper and sit in the fridge overnight, uncovered. Day of preheat the oven to 300*F.
Make the sauce by simmering all in a pot for 10 minutes and whisking together. Set aside. This can be done in advance. If you don’t want to make the sauce, use a high quality ketchup instead.
In a dutch oven over medium heat, add avocado oil and sear the brisket on both sides until golden brown and remove. In the same pan add the onions and cook until translucent, around 8 minutes. Salt as you go. Add minced garlic and cook another 2 minutes. Deglaze with red wine. Bring the red wine up to a simmer and reduce by half, around 4 minutes.
Add the tomato sauce, mustard, chili powder, paprika, bay leaves and beef stock to the pot. Add the beef back and bring up to a simmer (make sure the liquid comes up ¾ of the side of the brisket). Cover with a lid and transfer to the oven. Cook for 2 hours. Remove from the oven, flip, and cook another 2 hours. (If you want to slice it instead of shred it, take it out after 3 hours)
Remove from the oven and test for fork tenderness. If it is fork tender, remove and shred. Add back to the sauce and simmer 10 minutes stovetop to coat thoroughly in the sauce and serve. If it isn’t fork tender yet, place back in the oven for another hour.
