Add the flank steak, onion, garlic, bay leaves, salt, and black pepper to a large pot, filling the pot with enough cold water to cover the steak. Bring it to a boil.
Once it reaches a boil, immediately reduce the heat to low. Cover the pot with a lid and let it simmer for approximately 2 hours, or until the steak is fork tender.
Carefully remove the steak from the pot and let it cool before shredding. Strain the broth into a clean jar and save it for later use.
Add 2 tablespoons of olive oil to a large skillet or Dutch oven set over medium heat. Add the 1 large diced onion, 1 red bell pepper, and 1 green bell pepper to the hot oil and sauté until the vegetables are softened, about 4 minutes. Stir in 4 cloves of minced garlic and cook until fragrant.
Add 1-2 tablespoons of tomato paste, 1 tablespoon of oregano, 1 teaspoon cumin, 1 teaspoon paprika, 1 teaspoon salt, and 1 teaspoon pepper. Cook for an additional 2-3 minutes, stirring often, until the spices become fragrant.
Stir in 1½ cups of beef broth, 1 cup of dry white wine (or extra beef broth), and 1 can of tomato sauce. Bring the mixture to a low boil, then reduce the heat to low and simmer for 15 minutes or until the sauce has reduced.
Add the shredded beef to the sauce along with 1 cup of olives (or 2-3 tablespoons of capers, if using). Mix well so the meat is evenly coated. Cook for an additional 5 minutes or until the beef is heated through.
Serve with warm yellow or white rice, black beans, and plantains, and garnish with cilantro, if desired.