In a bowl combine the egg, bread crumbs, 1/2 cup of the applesauce, onion, 1 teaspoon of the prepared mustard, celery flakes, salt, and pepper.
Add ground beef, mix well.
Shape into a round loaf in a shallow baking pan.
Make a depression in top of loaf.
Combine the remaining 1/2 cup applesauce and 1 teaspoon mustard; stir in the brown sugar, vinegar, and allspice.
Spoon into depression.
Bake at 350° for 50 to 60 minutes.