Mix salt, pepper, garlic powder, and onion powder. Then mix in lemon or lime juice to form a paste.
Coat the top and sides of roast with paste. Put roast in cooking pan and add vegetables (if using)
Put roast in oven and cook for about 5-6 hours (cooking time will vary depending upon the size and thickness of your roast as well your oven).
You'll know your roast is done when it falls apart with a fork and the paste has formed a nice crust. If it's still tough when you pull it out of the oven, pop it back in and cook some more.