Preheat your oven to 350°F (175°C). This ensures that the meatloaf cooks evenly.

In a large mixing bowl, combine the ground beef, breadcrumbs, diced onion, minced garlic, Worcestershire sauce, ketchup, salt, pepper, thyme, and milk.

Add the egg to the mixture. The egg acts as a binder, helping to hold the meatloaf together.

Using your hands, mix the ingredients gently until just combined. Overmixing can lead to a dense meatloaf.

Transfer the meat mixture into a loaf pan, pressing it down gently to shape it into a loaf.

Place the loaf pan on a baking sheet to catch any drippings during cooking.

Bake in the preheated oven for 50 minutes.

While the meatloaf is baking, prepare the glaze by mixing together ketchup, brown sugar, and apple cider vinegar in a small bowl.

Stir until the sugar is dissolved and the mixture is smooth.

After 50 minutes, remove the meatloaf from the oven and brush the glaze evenly over the top.

Return the meatloaf to the oven and bake for an additional 10-15 minutes, or until the internal temperature reaches 160°F (70°C).

Once cooked, remove from the oven and let it rest for 10 minutes before slicing. This helps the juices redistribute.