1. Trim any visible fat from the meat. Rinse the meat, and pat it dry with paper towels. Sprinkle both sides with pepper.
2. Coat a large cast-iron skillet or Dutch oven with nonstick cooking spray, and preheat over medium-high heat. Place the meat in the skillet, and brown it for 2 minutes on each side. Remove the skillet from the heat, and spread the onions on the meat. Pour the beef broth in the bottom of the skillet, cover the skillet tightly, and bake at 325°F for 2 hours.
3. Remove the skillet from the oven, and carefully remove the cover. (Steam will escape.) Place the carrots and prunes around the meat, and sprinkle the meat, carrots, and prunes with the cinnamon, salt, and lemon juice. Cover the skillet tightly, and return it to the oven for another 30 minutes, or until the meat and carrots are tender. Transfer the meat, carrots, and prunes to a serving platter, and keep warm.
4. To make the gravy, pour the meat drippings into a fat separator cup. (If you don't have a separator cup, pour the drippings into a bowl, add a few ice cubes, and skim off the fat once it rises and hardens.) Pour the fat-free drippings into a 1-cup measure, and add enough water to bring the volume up to 3/4 cup.
5. Return the drippings mixture to the skillet, and add the brown sugar. Bring the mixture to a boil over medium heat, and cook and stir for 1 minute, or until the sugar is dissolved.