This is my favorite recipe from my mom. Recipe reads:

Grannie Annie’s Polynesian Beef

1 6oz cans unsweet pineapple juice
1 small can crushed or diced pineapple, undrained
3 tbs. soy sauce
3 tbs brown sugar
1 envelope dry onion soup mix
1 beef roast (about 4 lb)
1/4 c each diced red & green pepper & diced onions

Mix ingredients. Pour over beef. You can cook this either in the oven or crockpot.
Oven: 350 oven 2 hrs take out and slice or shred beef, return to oven cook ½ hr longer
Crockpot: 8-10 hours on low, until beef is tender. Slice or shred beef, return to crockpot and cook ½ hour more.
Serve over rice.