Cut the rack of ribs in half with a large knife or poultry scissors and make sure they fit all the way in the cooker with the lid on. Now take them out.
Place the sliced onion in the cooker, then put the ribs back in.
Combine the brown sugar, chili powder, pepper, and salt in a small bowl.
Rub this mixture all over the ribs. Wash your hands well.
Combine the chili sauce, balsamic vinegar, Worcestershire sauce, garlic, Tabasco and liquid smoke in a bowl.
Pour this mixture evenly over the top of the ribs.
Cover and cook on low for 7 to 8 hours, or until the meat is tender and has begun to pull away from the bone. The longer you cook the meat, the tenderer it will become.
Before serving, flip the ribs over a few times to get all sides nice and saucy.