Begin by trimming any excess fat from the beef brisket, leaving about 1/4 inch to retain moisture during cooking. Next, rub the brisket thoroughly with a mixture of smoked paprika, ground cumin, black pepper, and salt to infuse it with flavor. Allow the spice mixture to set for a few minutes while you get your aromatics ready.

In a large skillet, heat a tablespoon of oil over medium heat and add the thinly sliced onions. Sauté the onions for 15-20 minutes until they are deeply caramelized, turning them golden brown and releasing delicious aromas. Once caramelized, add the minced garlic and sauté for an additional 2-3 minutes, just until fragrant, and then remove from heat.

Transfer the caramelized onions and garlic into a slow cooker or Dutch oven, creating a cozy base for your brisket. Place the seasoned brisket on top of the onion mixture. In a separate bowl, mix the brown sugar, soy sauce, beef broth, and apple cider vinegar together, then pour this sweet and savory glaze over the brisket.

If using a slow cooker, cover and cook the brisket on low for 8-10 hours. For a Dutch oven, preheat your oven to 300°F (150°C), cover the pot and bake for 3-4 hours.

Once cooked, remove the brisket from the heat and let it rest for 20 minutes. Then, using two forks, shred the brisket into tender pieces, mixing it back into the remaining cooking liquid.