Position an oven rack in the center and preheat the oven to 350°F (175°C). Grease a loaf pan or line a rimmed baking sheet with foil. Grate the onion and mince the garlic.
Place the panko breadcrumbs in a large mixing bowl, pour the whole milk over them, and stir once to coat. Let sit for 5 minutes until the bread softens into a loose paste.
Add the beaten eggs, Worcestershire sauce, ¼ cup ketchup, grated onion, minced garlic, parsley, garlic powder, dried thyme, salt, and pepper to the panade. Stir until evenly blended.
Add the ground beef and mix gently with clean hands or a fork just until combined and no dry streaks remain. Do not overmix.
Transfer the mixture to the prepared loaf pan and press in gently, or shape into a 9 by 5 inch loaf on the lined baking sheet. Smooth the top with the back of a spoon.
Stir together the ½ cup ketchup, brown sugar, apple cider vinegar, and Dijon mustard until smooth. Brush about two-thirds over the top and sides of the loaf, reserving the rest.
Bake for 45 minutes. Remove, brush on the remaining glaze, and return to the oven. Bake for 10 to 15 minutes more, until an instant-read thermometer reads 160°F (71°C).
Let the meatloaf rest for 10 minutes before slicing. Lift from the pan using the parchment or drain excess fat first, then slice into thick, even pieces and serve.