Preheat your oven to 350°F. Line a rimmed baking sheet with parchment paper or foil for easier cleanup.
Heat olive oil in a medium skillet over medium heat. Add the chopped onion and sauté for 5 to 7 minutes, stirring occasionally, until softened and lightly golden. Transfer to a plate and let cool.
In a large mixing bowl, combine the ground beef, cooled onion, eggs, garlic, ketchup, parsley, breadcrumbs, milk, salt, Italian seasoning, and black pepper. Mix just until combined.
Shape the mixture into a loaf about 8 inches long, 4 inches wide, and 3 inches tall on the prepared baking sheet.
Bake uncovered for 40 minutes.
While it bakes, make the sauce by stirring together ketchup, white vinegar, brown sugar, garlic powder, and onion powder in a small bowl.
Remove the loaf from the oven and spread the glaze evenly over the top. Return it to the oven and continue baking for 20 more minutes. This Meatloaf Recipe is ready when the internal temperature reaches 160°F.
Let the meatloaf rest for 10 to 15 minutes before slicing and serving.