Barbacoa (Crock Pot)

FOR THE BEEF: 3 lb. Pleasant Valley chuck or rump beef roast 1 onion, chopped 1/4 cup apple cider vinegar 6 garlic cloves, chopped 2 T. whole black peppercorns 2 bay leaves FOR THE SAUCE: 1 large (1 lb.) can tomato sauce 1/2 pound green chiles, roasted, skinned and...