Place roast in large roasting pan. Rub with garlic cloves and ketchup. Sprinkle on garlic powder, onion powder, and paprika.

Slice onions into quarters and place on top of roast.

Pour soda over the roast.

Cover and bake at 350 degrees for three and a half to four hours, basting twice in middle of cooking time.

Allow to cool and slice meat into thin slices. Place back into sauce to rewarm.