Preheat your oven to 350°F.
In a large mixing bowl, combine all the ingredients for the meat mixture: ground beef, breadcrumbs, chopped onion, milk, eggs, Worcestershire sauce, garlic powder, salt, black pepper, and dried thyme. Mix until just combined.
Transfer the mixture into a loaf pan and mold it into a loaf shape.
In a separate bowl, whisk together the ketchup, brown sugar, and apple cider vinegar to make the glaze.
Place the shaped meatloaf in the preheated oven and bake for 60 minutes. After 30 minutes, brush half of the tangy glaze over the top.
Let the meatloaf rest for 10 minutes before slicing and serving with the remaining glaze on the side.