Cooking Steps
Combine ground beef, onion, milk, bread crumbs and egg in a large bowl. Season with salt and pepper.
Lightly grease a 9×5-inch loaf pan.
Transfer ground beef into prepared loaf pan.
Mix ketchup, brown sugar, and mustard together in a small bowl until well combined.
Pour the sauce over the meatloaf and spread evenly over the top.
Preheat the oven to 350 degrees F (175 degrees C).
Bake the meatloaf in the preheated oven until the center is no longer pink (about 1 hour).
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