Mexican Beef

1 (3 or 4 pound) rump roast
2 roasted green chiles, skins and seeds removed,
    diced, or 1 (4 ounce) can diced green chiles
1 (16 ounce) can tomatoes and green chiles
1 (14 ounce) can tomatoes and jalape?os
1 (8 ounce) can tomato sauce
1 (6 ounce) can tomato paste
1 large onion, diced

Cook slowly all day. Remove top fat. Shred meat. This is great in flour tortillas. Serve with sour cream, if desired.