Preheat the oven to 425 degrees . Place the ham in a roasting pan. In a large saucepan, bring the broth, onion, sugar, bourbon, thyme, garlic and black and red pepper to a boil; stir until the sugar dissolves. Boil 3 minutes, then pour over the ham. Roast 30 minutes. Baste the ham with the pan juices; tent with foil. Reduce the heat to 325 degrees and roast, basting with the pan juices every hour, until an instant-read thermometer inserted into the thickest part of the ham (not touching bone) registers 145 degrees , about 2 1/2 hours.
Strain the pan juices into a large pitcher and stir in the lemon juice. Slice the ham thinly; serve with the pan juices.