1-First Step: Mise en place Preheat the oven to 350°F. Line a rimmed baking sheet with parchment paper or foil for easy cleanup. Finely chop 1 medium onion to yield about 1 cup, measure the panko, and whisk the eggs and milk together in a small bowl. Preparing ingredients ahead saves time and keeps the process smooth.

2-Second Step: Saute the aromatics Heat 1 teaspoon oil in a medium skillet over medium heat. Add the chopped onion and cook, stirring occasionally, until softened and golden, about 5 to 7 minutes. Remove from heat and set aside to cool slightly before adding to the meat mix. Sauteing the onion reduces sharpness and helps the loaf have a mellow, cooked-onion flavor.

3-Third Step: Combine the meat mixture In a large bowl combine the following: 2 lbs ground beef, the cooled sautéed onion, 3 minced garlic cloves, 2 large eggs, 2 tablespoons ketchup, 3 tablespoons chopped fresh parsley, 3/4 cup Panko breadcrumbs, 1/3 cup milk, 1 teaspoon Italian seasoning, 1 teaspoon salt, and 1/2 teaspoon ground black pepper. Gently mix with your hands or a spoon just until ingredients are combined. Do not overmix; overworking the meat creates a dense loaf. If swapping in ground turkey or sausage for half the beef, fold those in gently at this stage.

4-Fourth Step: Shape the loaf Shape the mixture into a free-form loaf approximately 8 inches long, 4 inches wide, and 3 inches tall on the prepared baking sheet. Press lightly to compact but avoid packing it tight. Free-form baking on the sheet gives crisp edges and cooks a bit faster than a loaf pan.

5-Fifth Step: Initial bake Bake uncovered for 40 minutes at 350°F. This gives the interior a head start while the outside firms up. If using a loaf pan instead, line it with parchment, press the meat gently into the pan, increase oven temperature to 375°F, and adjust cooking time upward as noted in the tips below.

6-Sixth Step: Prepare and apply the glaze While the loaf bakes, whisk together the glaze: 3/4 cup ketchup, 1 1/2 teaspoons white vinegar, 2 tablespoons brown sugar, 1/2 teaspoon garlic powder, and 1/2 teaspoon onion powder. After 40 minutes, spread the glaze evenly over the top of the meatloaf and return it to the oven.

7-Seventh Step: Finish baking Bake an additional 20 minutes, or until the internal temperature reaches 160°F for beef (165°F if using poultry). Use an instant-read thermometer inserted into the center of the loaf to check doneness. Visual cues like clear juices and a firm surface can help when a thermometer is not available, but the thermometer is the safest check.

8-Final Step: Rest and serve Let the meatloaf rest for 10 to 15 minutes before slicing. Resting allows juices to redistribute, making clean slices and a juicier bite. Slice with a sharp knife and serve with mashed potatoes, roasted vegetables, or a fresh salad.