Pat the brisket dry with paper towels. Combine kosher salt, black pepper, chili powder, cumin, garlic powder, onion powder, and smoked paprika in a small bowl. Rub the spice mixture evenly over all sides of the brisket and let sit at room temperature for 20–30 minutes (or refrigerate up to overnight).

Sear brisket

Preheat oven to 300°F (150°C). Heat a large ovenproof Dutch oven or heavy-bottomed pot over medium-high heat and add 2 tablespoons vegetable oil. When oil shimmers, sear the brisket fat-side down for 4–5 minutes until deeply browned, then sear the other sides 3–4 minutes each. Remove brisket and set aside.

Sauté aromatics

Reduce heat to medium. Add the sliced onion to the pot and sauté 4–5 minutes until softened and beginning to brown, scraping up browned bits. Add smashed garlic and cook 30–60 seconds until fragrant.

Deglaze and braise

Pour in beef broth and soy sauce to deglaze, scraping up any fond from the bottom of the pot. Stir in apple cider vinegar and add the bay leaf. Nestle the seared brisket back into the liquid, fat side up; the liquid should come about 1/3 to 1/2 way up the brisket. Bring to a gentle simmer on the stovetop.

Oven braise

Cover the pot tightly with a lid and transfer to the preheated oven. Braise for 3 to 3 1/2 hours, or until the brisket is fork-tender and reaches an internal temperature of about 200°F (93°C). Check once halfway and spoon some cooking liquid over the top; if the liquid is very low, add up to 1/2 cup more broth.

Rest and shred

Remove the pot from the oven and transfer the brisket to a cutting board. Let rest 15–20 minutes, reserving the cooking liquid. Using two forks, shred or thinly slice the brisket across the grain. If shredding, toss pieces with a few tablespoons of reserved braising liquid to keep moist. Taste and adjust seasoning with salt and pepper if needed.

Tacos & Finish

Warm tortillas

Warm flour tortillas on a dry skillet over medium heat for 20–30 seconds per side until pliable and lightly charred in spots. Alternatively, wrap stacks of 4 tortillas in a damp paper towel and microwave 30–45 seconds until warm.

Assemble tacos

Place 2–3 tablespoons of shredded brisket in the center of each warm tortilla. Top with a small spoonful of diced red onion, a sprinkle of chopped cilantro, pickled jalapeños if using, and crumbled queso fresco or cotija. Squeeze a wedge of lime over each taco and add hot sauce or salsa verde to taste.

Serve

Serve tacos immediately with extra braising liquid on the side for drizzling or dipping. Leftover brisket can be refrigerated 3–4 days or frozen up to 3 months.