Preheat your oven to 350°degrees F.
In a large bowl, combine the egg, onion, breadcrumbs, Worcestershire sauce, half the tomato sauce, half the mustard, 1 1/2 tsp of the garlic powder, 1/2 tsp salt and 1/4 tsp pepper. Mix well and let it sit for a minute or two to let the liquids combine with the breadcrumbs.
8 Oz. Tomato Sauce, 1/2 C Bread Crumbs, 1/2 C Diced Onion, 1 Egg, 2 tsp Mustard, 2 tsp Garlic Powder, 1/2 Tbsp Worcestershire Sauce, Salt and Pepper to Taste
With *clean* hands, add the ground beef to this mixture and knead everything together for 1-2 minutes until very well combined.
1 Lb Ground Beef
Shape the meat mixture into a loaf shape, roughly 4-5 inches wide, and place it into the center of your baking pan or dish. Note: make sure there is open space between the leatloaf and the edges of the dish. You want room for the grease to flow away from the meatloaf, so it isn't swimming in the juices. Bake this, uncovered, at 350°F on the bottom shelf for 45 minutes.
While it bakes, prepare the sauce for the top. Mix the remaining tomato sauce, mustard and garlic powder together. Season with salt and pepper to taste.
After 45 minutes of baking, baste the meatloaf evenly with the sauce.
Bake another at 350°F for another 15 minutes, or until the internal temperature reaches 160°F*.
Remove from the oven and let it rest for 10 minutes before slicing into inch-thick pieces.