French Dip Roast (Crock Pot)

1 large onion, quartered and sliced
1 (3 lb) beef roast, fat trimmed
1/2 cup water
1 (1 ounce) package au jus mix
1/8 teaspoon seasoned pepper

Place onion in crock pot.
Place meat on top of onion.
In a small bowl, stir water, au jus mix and seasoned pepper until blended.
Pour over roast.
Cover and cook on High for 5 to 6 hours; or on Low for 10 to 12 hours, or until tender.
Remove meat from liquid.
Let stand for five minutes before thinly slicing across grain.
Strain liquid and make gravy.