Season the flank steak with salt and pepper. Set the Instant Pot to "Saute" mode and add the olive oil. Once hot, sear the flank steak on both sides until browned, then remove and set aside.
In the same pot, add the chopped onion, bell peppers, and garlic. Saute for a few minutes until the vegetables are softened.
Stir in the crushed tomatoes, beef broth, cumin, paprika, oregano, salt, black pepper, cayenne pepper, bay leaves, olives, capers, tomato paste, and white vinegar.
Return the seared flank steak to the Instant Pot, nestling it into the sauce.
Close the Instant Pot lid and set to "Manual" or "Pressure Cook" mode for 60 minutes on high pressure.
Once the cooking time is complete, allow for a natural pressure release for 10-15 minutes, then carefully release any remaining pressure.
Remove the flank steak from the Instant Pot and shred it using two forks.
Return the shredded beef to the sauce in the Instant Pot and stir to combine.
Serve the Ropa Vieja over cooked white rice, garnished with fresh cilantro or parsley.