Preheat the oven to 350°F (175°C). Grease a loaf pan or line it with parchment paper.
Combine the meat mixture: In a large bowl, mix ground beef, breadcrumbs, egg, chopped onion, minced garlic, milk, ketchup, Worcestershire sauce, thyme, smoked paprika, salt, and pepper. Mix until just combined; avoid overmixing to keep the meatloaf tender.
Shape the loaf: Press the meat mixture into the prepared loaf pan, shaping the top smoothly.
Prepare the topping: In a small bowl, combine ketchup, brown sugar, and mustard. Spread the mixture over the top of the meatloaf.
Bake for 55-60 minutes or until the internal temperature reaches 160°F (71°C).
Cool and serve: Let the meatloaf rest for 10 minutes before slicing. Serve with mashed potatoes or a side of roasted vegetables.