Prepare the Flank Steak: Season the flank steak generously with salt and black pepper on both sides.
Sear the Meat: In a large pot or Dutch oven, heat 2 tablespoons of oil over medium-high heat. Add the flank steak and sear it on both sides until browned, about 4-5 minutes per side.
Sauté Vegetables: Remove the steak from the pot, then lower the heat slightly and add remaining oil if necessary. Sauté onions and bell peppers until they soften before adding minced garlic.
Build Flavor: Stir in tomato paste along with dried oregano, cumin, paprika, allspice, cloves, grape juice, chicken broth, crushed tomatoes, carrot, celery, and bay leaves ensuring everything is well combined.
Braise the Flank Steak: Return seared flank steak back into the pot; bring mixture to a simmer then cover tightly and reduce heat to low allowing it to braise for approximately 80 minutes until tender.
Final Touches: After cooking is complete; remove steak from pot and shred using two forks before returning it back into sauce along with olives, pimentos, capers if using; stir well before serving over rice garnished with cilantro or parsley.