1 (2 1/2 pound) flank steak, cut in half
(or chuck steak or roast)
1 bay leaf
1/4 cup fresh lime juice
1/4 cup fresh lemon juice
3 cloves garlic, finely chopped
Salt and pepper, to taste
1/2 cup olive oil
1 large onion, cut in half and each half thinly sliced
2 tablespoons finely chopped fresh parsley
Place the beef and bay leaf in a large saucepan, cover with salted water, and cook over low heat, covered, until the meat is tender, 1 to 1 1/2 hours (chuck roast may take a little longer). Remove the meat from the stock and allow to cool at room temperature (save the stock for another use).
When the meat is cool, cut into 2-inch chunks, shred it using your fingers, and place in a nonreactive bowl. Add the citrus juices, garlic, salt, and pepper, cover and refrigerate at least 1 hour, or overnight.
Remove the meat from the marinade and squeeze out the excess liquid. In a large skillet, heat the oil over medium-high heat until fragrant and cook the beef shreds, stirring 6 to 8 minutes. Add the onions and cook until the beef is crisp, another 5 minutes. Sprinkle with the parsley and serve over white rice.