Combine tomato sauce, water, mustard, and vinegar in a bowl.

In a separate bowl, mix ground veal, bread crumbs, egg substitute, chopped onion, and pepper.

Add 1/4 of the tomato sauce mixture to the veal mixture and combine thoroughly.

Shape the mixture into a loaf and place it in a loaf pan.

Pour enough of the remaining tomato sauce over the top of the loaf to coat it.

Bake in a preheated oven at 350°F (175°C) for 1 hour.

Baste the meat loaf frequently during baking with the tomato sauce.

Heat the remaining sauce and serve it over sliced meat loaf.