Trim the excess fat from the beef brisket, leaving about 1/4 inch for moisture and flavor retention. Rub with smoked paprika, ground cumin, black pepper, and salt.

In a large skillet, heat oil over medium heat. Sauté sliced yellow onions for 15-20 minutes until golden brown. Add minced garlic and sauté for an additional 2-3 minutes.

In a slow cooker or Dutch oven, layer the caramelized onion and garlic mixture at the bottom. Place the seasoned brisket on top. Mix together brown sugar, soy sauce, beef broth, and apple cider vinegar, and pour over the brisket.

Cook the brisket on low for 8-10 hours in a slow cooker or bake at 300°F (150°C) for 3-4 hours in a Dutch oven until fork-tender.

Remove the brisket and let it rest for 20 minutes. Shred into pieces and mix back into the cooking liquid.