Preheat oven to 350 degrees. Place ground beef, onion, bread cubes (soaked in milk), ketchup, beaten eggs, bread crumbs in a large bowl and mix together with your hands. Put mixture into a casserole dish. Mold together in a loaf.
Pour tomato sauce over loaf. In a small bowl, mix together ketchup, mustard, and brown sugar. Spread mixture over top. Sprinkle with salt and pepper. Add a small amount of water if necessary along side of pan.
Cover and bake in 350 degree oven for approximately 1 1/2 hours. Check half way through baking time to be sure there's enough liquid in bottom of pan so it won't burn. Enjoy with mashed potatoes.