Preheat the oven to 350°F (175°C). Line a 9 by 5 inch loaf pan with parchment paper or lightly grease it.

Heat a small skillet over medium heat. Add the diced onion with a pinch of salt and sauté for 3 minutes until softened.

Add the minced garlic to the skillet and cook for 1 minute until fragrant. Transfer to a plate to cool.

In a large mixing bowl, place the cold ground beef and ground pork. Break them up gently with your hands without overmixing.

In a small bowl, whisk together the eggs, whole milk, 1/4 cup ketchup, Worcestershire sauce, and Dijon mustard.

Add the panko breadcrumbs, cooled onion and garlic mixture, and wet ingredients to the meat. Season with kosher salt and black pepper.

Fold the ingredients gently with your hands until just combined, about 1 minute. Avoid overmixing.

Press the meat mixture evenly into the prepared loaf pan, smoothing the top with your hands or a spatula.

In a small bowl, whisk together 1/2 cup ketchup, brown sugar, and apple cider vinegar to make the glaze.

Brush the glaze evenly over the top of the meatloaf, reserving about 2 tablespoons for later. Place the pan on a sheet pan to catch drips.

Bake for 45 minutes, or until an instant read thermometer inserted into the center reads 160°F (71°C).

Remove the meatloaf from the oven and brush with the remaining glaze. Let it rest in the pan for 5 minutes before slicing.