Meatloaf with Sweet and Sour Sauce

1 (8 oz.) can tomato sauce
1/4 c. brown sugar, packed
1/4 c. cider vinegar
1 tsp. prepared mustard
1 egg, slightly beaten
1 onion, minced
2 stalks celery, chopped
1/2 green pepper, chopped
1/4 c. Italian seasoned bread crumbs or crushed crackers
2 lbs. ground sirloin
1/2 tsp. Salt
1/4 tsp. black pepper

In a saucepan mix tomato sauce, brown sugar, vinegar and mustard. Cook until sugar is dissolved. Set aside. Take onion, celery, green pepper and  1 tablespoon water; put in bowl. Put Saran wrap over them and put in microwave to soften. Combine egg with vegetables (celery, onion, green pepper), crackers, salt, black pepper, meat and 1/2 cup tomato sauce mixture. Mix thoroughly. Shape into loaf. Put into baking dish and pour remaining tomato sauce mixture over meatloaf. Bake 350 degrees covered  for 1 hour. Baste occasionally. If sauce thickens, add 1/4 cup water to
sauce. Serve sauce separate. Serves 6.