Preheat the Oven: Preheat your oven to 350°F (175°C). Grease a loaf pan or line it with parchment paper.
Mix the Ingredients: In a large bowl, combine the ground beef, egg, chopped onion, breadcrumbs, milk, ketchup, Worcestershire sauce, salt, pepper, and thyme. Use your hands or a spoon to mix everything until just combined.
Shape the Meatloaf: Transfer the meat mixture to the loaf pan, pressing it down evenly. Smooth out the top and spread the ½ cup of ketchup over the surface of the meatloaf.
Bake the Meatloaf: Place the meatloaf in the preheated oven and bake for 1 hour, or until the internal temperature reaches 160°F (70°C). Allow the meatloaf to rest for 10 minutes before slicing and serving.
