Step 1: Prepare the Spice Rub

In a small bowl, combine all the rub ingredients: brown sugar, smoked paprika, chili powder, garlic powder, onion powder, cumin, mustard powder, kosher salt, and black pepper. Mix thoroughly until you have a uniform, fragrant spice blend.

Step 2: Season the Brisket Generously

Pat the brisket dry with paper towels. This is a crucial step to ensure you get a good sear. Sprinkle the spice rub all over the brisket, using your hands to press it firmly into the meat on all sides. Be generous; you want a thick, even coating. Don’t be shy—this crust is a major flavor component.

Step 3: Sear the Brisket (The Most Important Step!)

Heat the olive oil in a large, heavy-bottomed skillet or Dutch oven over medium-high heat. The pan should be very hot. Carefully place the seasoned brisket in the skillet, fat-cap side down. Sear for 4-5 minutes per side, until a deep, dark brown crust has formed. Do not move the brisket while it’s searing to allow the crust to develop. This process, known as the Maillard reaction, creates hundreds of new flavor compounds and adds an incredible depth that you cannot achieve otherwise. Once seared on both sides, remove the brisket from the skillet and set it aside.

Step 4: Prepare the Slow Cooker Base

Place the thick slices of onion and the smashed garlic cloves on the bottom of your slow cooker. This creates a “rack” for the brisket to sit on, preventing it from boiling on the bottom and allowing it to steam evenly. It also infuses the braising liquid with aromatic flavor.

Step 5: Combine the Braising Liquid

In the same skillet you used to sear the brisket (do not wipe it out!), reduce the heat to medium. Pour in the beef broth to deglaze the pan, using a wooden spoon to scrape up all the browned bits (called “fond”) from the bottom. These bits are concentrated flavor. Whisk in the BBQ sauce, apple cider vinegar, Worcestershire sauce, and liquid smoke until smooth. Bring the mixture to a gentle simmer for 1-2 minutes to allow the flavors to meld.

Step 6: The Low and Slow Cook

Place the seared brisket on top of the onions in the slow cooker, fat-cap side up. Pour the warm braising liquid from the skillet over and around the brisket. Secure the lid on the slow cooker. Cook on LOW for 8-10 hours or on HIGH for 4-5 hours. Low and slow is highly recommended for brisket, as it gives the connective tissue more time to break down, resulting in a more tender product. You’ll know it’s done when the meat is fork-tender and easily pulls apart.

Step 7: Shred the Beef and Create the Sauce

Carefully remove the brisket from the slow cooker and place it on a large cutting board or in a large bowl. It may fall apart as you lift it, which is a great sign! Let it rest for 10-15 minutes. While it rests, strain the cooking liquid from the slow cooker through a fine-mesh sieve into a saucepan, discarding the onions and garlic.

Using two forks, shred the beef, pulling against the grain. Discard any large, unrendered pieces of fat.

Bring the strained liquid in the saucepan to a boil over medium-high heat. Let it simmer and reduce for 10-15 minutes, or until it has thickened into a rich, glaze-like sauce. Stir in an additional 1/2 cup of BBQ sauce if you desire a thicker, more potent sauce.

Step 8: Combine and Serve

Return the shredded brisket to the now-empty slow cooker basin (or a large bowl). Pour about half of the reduced sauce over the meat and toss to coat everything evenly. Keep the remaining sauce on the side for serving. Your BBQ beef brisket is now ready for the tacos!