Preheat oven to 350°F. Season beef all over with salt and pepper. Heat oil in a medium oven-proof pot over medium-high heat. Add beef and cook, flipping once, until dark golden brown on both sides, 8 to 10 minutes; transfer to a plate. Add vinegar, cranberry sauce and orange juice to pot and bring to a boil, scraping up any browned bits. Return beef to pot, cover with foil, then lid and bake until falling-apart tender, about 2 hours, turning meat halfway through. Using two forks, shred beef and stir together with remaining liquid in the pot. Top each square of bread with some of the beef, garnish with zest and parsley and serve.
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