In a large bowl, combine the ground beef, bread crumbs, salt, ground black pepper, eggs, onion flakes and 1/2 of the can of tomato sauce. Mix together well and place into a 5x9 inch loaf pan.
Push the meatloaf down into the pan forming a well for the sauce around all the edges.
Bake at 350 degrees F (175 degrees C) for 40 minutes.
Meanwhile, in a small saucepan over medium heat, combine the remaining tomato sauce, brown sugar, vinegar, white sugar and mustard. Bring to a boil and remove from heat.
After meatloaf has cooked for 40 minutes, remove from oven and pour sauce over the top of the meatloaf.
Return to oven and bake at 350 degrees F (175 degrees C) for 20 more minutes. Let sit 5 minutes before removing from pan.
