Clean and trim excess fat from the roast; place in roaster. Completely cover roast with beef bouillon, add chopped onions and season with garlic powder, salt and pepper. Cover roaster with a lid or aluminum foil and bake at 350 degrees for several hours or until it is tender (about 4-5 hours). Reserve broth and fat drippings for gravy.
Remove roast from pan and make gravy. Mix cornstarch and water together to make a roux and add it to the roasting pan with reserved broth and drippings (I use a meat baister to get some of the fat off the top. Cook on the stove top over medium heat, stirring constantly until nice and thick.