Island Beef (Crock-Pot)

Recipe from The Best Slowcooker Cookbook Ever

2-2 1/2# beef  round steak, trimmed of fat
2 large onions, cut into 12 thin wedges each
1 (20oz) can unsweetened pineapple chunks, reserve juice
1/2c beef broth
5T red wine vinegar (divided as per directions)
3/4tsp garlic powder
3/4tsp seasoned salt
3/4 tsp sweet paprika
1/4tsp black pepper
1 green bell pepper, cut into 1" squares
1 red bell pepper, cut into 1" squares
3T brown sugar
1 1/2T cornstarch
2T soy sauce
2 large tomatoes cut into chunks

*cut beef into dtrips across grain, put into 3-4qt crockpot
*add onions, pineapple juice, broth, 3T vinegar, garlic powder, seasoned salt, paprika and black pepper; mix well; cover crock and cook on low 6h until beef is just tender
*increase to high and add bell peppers and brown sugar.  Mix cornstarch, soy and remaining vinegar.  Stir into crockpot and blend well.
*cook 45-60min until sauce thickens slightly.
*just before serving add pineapple chunks and tomato wedges