Slow-Cooked Pulled Pork Shoulder

INGREDIENTS

• 1 (3 pound) pork shoulder
• 4 cups water, or as needed
• 8 cups white vinegar, or as needed
• 1/4 cup kosher salt
• 1 large onion, cut into 8 wedges
• 1 tablespoon ground cumin
• 1 tablespoon ground mustard
• 1 tablespoon chili powder
• 1/2 cup brown sugar