Preheat your oven to 325°F (165°C).

Pat the brisket dry with paper towels and season both sides generously with salt and black pepper.

Heat the vegetable oil in a large oven-safe Dutch oven or heavy pot over medium-high heat.

Place the brisket in the pot and sear for about 5 to 7 minutes per side until a dark brown crust forms. Remove the meat and set it aside on a plate.

In the same pot, add the sliced onions and cook over medium heat for about 10 to 12 minutes, stirring often, until they are soft and golden brown.

Add the minced garlic and cook for another minute until fragrant.

Stir in the tomato paste, brown sugar, apple cider vinegar, beef broth, and fruit juice, scraping up all the browned bits from the bottom of the pot with a wooden spoon.

Add the bay leaves and dried thyme to the liquid.

Place the brisket back into the pot, nestling it into the onions and liquid, and arrange the carrot chunks around the meat.

Cover the pot with a tight-fitting lid and place it in the oven.

Bake for 3.5 to 4 hours, or until the meat is very tender when pierced with a fork.

Remove the brisket from the pot and let it rest on a cutting board for at least 20 minutes before slicing against the grain.

While the meat rests, strain the cooking liquid if you prefer a smooth sauce, or leave the onions in for a rustic feel and simmer if you want to thicken it further.

Pour the warm sauce over the sliced meat and serve immediately.