Heat 1 tablespoon of vegetable oil in a large heavy-bottomed pot or Dutch oven over medium-high heat. Season the flank steak generously with salt and pepper on both sides. When the oil is hot, add the steak and sear until deeply browned, about 4 minutes per side. Transfer the meat to a plate and set aside.

In the same pot, add the remaining tablespoon of oil. Add the sliced onions and bell peppers, cooking until they begin to soften, about 5-7 minutes. Add the minced garlic and cook for another 30 seconds until fragrant.

Pour in the white wine (if using) and scrape up any browned bits from the bottom of the pot. Add the diced tomatoes, tomato sauce, and beef broth. Stir in the oregano, cumin, smoked paprika, and bay leaves. Season with salt and pepper to taste.

Return the seared flank steak to the pot, nestling it into the sauce. Bring the mixture to a simmer, then reduce heat to low. Cover and cook for 3-4 hours, until the meat is very tender and easily pulls apart with a fork.

Once the beef is tender, remove it from the pot and place it on a cutting board. Using two forks, shred the meat along the grain into long strands (resembling 'old clothes'). Discard any tough pieces.

Return the shredded beef to the pot with the sauce. Add the sliced olives and capers. Stir well and simmer uncovered for an additional 15-20 minutes, allowing the sauce to reduce slightly and the flavors to meld.

Remove the bay leaves. Taste and adjust seasoning if needed. Stir in the fresh chopped cilantro just before serving. Serve hot over white rice, with black beans on the side and lime wedges for squeezing.