With sharp knife, cut each tenderloin lengthwise from end to end, being careful not to cut through to other side. Set aside.

Stuffing: In non-stick skillet, heat oil over medium heat; sauté onions, stirring frequently, for about 20 minutes or until deep golden brown. Stir in vinegar, salt and pepper; cook for 5 minutes. Remove from heat. Stir in bread crumbs, parsley and orange rind. Set aside.

Place filling along length of one tenderloin. Top with second tenderloin and tie with string. Place meat on rack set over a foil-lined roasting pan.

Glaze: In small bowl, combine mustard, honey and pepper; brush over pork. Roast in 375º F (190º C) oven for 40 minutes or until cooked through and juices run clear (internal temperature will be about 160º F/ 70º C).

Cover and let stand for 10 minutes before carving into ½ -inch (1 cm) thick slices.