Slow-Cooker Georgia Pulled Pork Barbecue

Prepare the roast: Put the quartered onions in the bottom of a 5- to 6-quart slow cooker. Mix the brown sugar, smoked paprika, 2 teaspoons salt and a pinch of black pepper and rub it all over the pork roast. Add the roast to the slow cooker on top of the onions.
Make the sauce: Chop the onion and puree in a blender. You may need to add a drop of water to the blender to help the onions completely puree. Place the pureed onion in a 2-quart saucepan with 1/4 cup water. Bring to a boil, then reduce the heat to medium low. Cook, stirring constantly, until the water has almost evaporated, about 5 minutes. Add the vinegar, tomato juice, 1/2 tablespoon black pepper, the garlic powder, cayenne and hot sauce and mix well. Increase the heat to medium high, return to a boil, then stir in the sugar. Remove from the heat.
Drizzle 1 cup sauce over the roast in the slow cooker. Continue to cook the remaining sauce over low heat for 30 to 40 minutes, allowing it to reduce by half. Then remove the sauce from the heat, allow it to cool completely and refrigerate for later use.
Meanwhile, cook the roast in the slow cooker on low for 8 to 12 hours, checking after 8 hours for tenderness. Remove the meat and onions from the slow cooker. Discard the onions and finely shred the pork, using two forks. Reserve the juices from the slow cooker to add to the meat for desired juiciness. Season with salt and pepper to taste. Serve on buns with a little mustard and coleslaw.