Pat the skirt steak dry with paper towels. Season generously on both sides with salt, black pepper, smoked paprika, garlic powder, and cayenne pepper (if using).

Heat 1 tbsp olive oil in a large skillet over medium-high heat until shimmering. Sear the skirt steak for 2-3 minutes per side until well-browned. This step adds significant flavor.

Remove the steak from the skillet and set aside. Add another 1 tbsp olive oil to the same skillet. Add the sliced onion and bell peppers and sauté for 5-7 minutes until slightly softened. Add the minced garlic and cook for another minute until fragrant.

Transfer the seared skirt steak to the bottom of your 6-quart (or larger) slow cooker. Top with the sautéed onions, bell peppers, and garlic.

In a small bowl, whisk together the beef broth, Worcestershire sauce, soy sauce, dried oregano, and ground cumin. Pour this mixture over the steak and vegetables in the slow cooker.

Cover the slow cooker and cook on LOW for 7-8 hours or on HIGH for 3.5-4 hours, until the steak is very tender and easily shreddable with a fork.

Carefully remove the steak from the slow cooker and place it on a cutting board. Shred the steak using two forks, or slice against the grain into desired pieces. If you want to thicken the sauce, whisk together cornstarch and cold water in a small bowl to create a slurry. Stir the slurry into the liquid in the slow cooker. Turn the slow cooker to HIGH (if not already) and cook for another 15-20 minutes, stirring occasionally, until the sauce has thickened.

Return the shredded or sliced steak to the slow cooker and toss to coat with the sauce. Garnish with fresh parsley or cilantro before serving.