Pulled Pork with Tangy Barbecue Sauce

Ingredients

• One 5- to 6-pound bone-in pork butt (sometimes called Boston butt; see note)
• 4 tsp salt
• 1 tbsp paprika
• 1 tbsp ground cumin
• 1 tbsp garlic powder
• 1 tbsp dry mustard
• 1 tbsp dark brown sugar, packed
• 1 tsp freshly ground black pepper
• 1 cup plus 2 tablespoons ketchup
• 3/4 cup cider vinegar
• 3/4 cup dark brown sugar, packed
• 1/4 cup plus 2 tablespoons spicy brown mustard or coarse-grain mustard
• 2 garlic cloves, minced
• 1/2 tsp cayenne pepper
• 3/4 cup water, for deglazing the roasting pan
• 12 hamburger buns (lightly toasted and buttered, if desired)