Preheat the oven to 350 degrees F (175 degrees C).

Combine ground beef, bread crumbs, 1/2 can tomato sauce, eggs, dried onion, salt, and black pepper until well mixed; transfer to a 9x5-inch loaf pan.

Push down meatloaf into the pan forming a well for sauce around all edges.

Bake in the preheated oven for 40 minutes.

Meanwhile, combine remaining 1/2 can tomato sauce, white sugar, brown sugar, vinegar, and mustard in a small saucepan over medium heat; bring to a boil, then remove from heat.

Pour sauce over top of meatloaf after 40 minutes of baking.

Return to oven; continue baking 20 minutes more. Let sit 5 minutes before removing from pan.