Rinse and pat dry the pork roast. Place onions in the slow-cooker or pressure cooker. In a small bowl, combine brown sugar, paprika, kosher salt and pepper; mix thoroughly. Rub mixture all over roast and place the roast on top of the onions.
In a medium bowl, combine vinegar, Worcestershire, red pepper flakes, sugar, mustard, garlic salt and cayenne pepper; whisk to combine. Pour over roast.
CROCK-POT DIRECTIONS: Cover the pork in the slow cooker and cook on low for 4-5 hours, adding about 30-40 minutes for each additional pound if you're multiplying the recipe. Shred with tongs and allow the shredded pork to rest in the cooking liquids until ready to serve. Serve warm on your favorite rolls.
PRESSURE COOKER DIRECTIONS: Seal the pressure cooker; cook on high for 60-90 minutes, (The cooking time is 90 minutes for the Insta-Pot, but I've been told that it requires less time for a stove-top pressure cooker.) check to see if it is shreddable. Cook an additional 30-40 minutes as needed. Shred with tongs and allow the shredded pork to rest in the cooking liquids until ready to serve. Serve warm on your favorite rolls. Enjoy!
FREEZER MEAL: This makes a great freezer meal. Once the meat is cooked and shredded, let it cool then store it in an airtight freezer bag. Let it thaw completely in the refrigerator prior to reheating.