Heat 1 tablespoon olive oil in a skillet over medium heat. Add the minced onion and cook for 4-5 minutes until softened and translucent.
In a large mixing bowl, combine ground beef, sautéed onions, 1 large egg, 1/4 cup bread crumbs, 1 tablespoon ketchup, 1 teaspoon Dijon mustard, 1 teaspoon seasoning salt, 1/2 teaspoon garlic powder, freshly chopped parsley, and 1/2 cup milk. Mix gently until just combined.
Shape the mixture into a loaf about 7 inches long and 3-4 inches wide to fit your air fryer basket.
Whisk together 2 tablespoons ketchup, 2 teaspoons brown sugar, 1 teaspoon Dijon mustard, and 1/2 teaspoon garlic powder until smooth. Spread half of the glaze evenly over the top of the meatloaf.
Place the meatloaf in the air fryer basket. Cook at 350°F (175°C) for 20 minutes. Then, spread the remaining glaze on top and cook for another 10-15 minutes until internal temperature reaches 160°F (71°C) and glaze is caramelized.
Remove the meatloaf and let rest for 5-10 minutes before slicing. Serve with your favorite sides.