Best ever meatloaf

I am sure everyone has their own favorite recipe for meatloaf but this is one of my new favs to make.

2 lbs ground beef ( you can also used ground turkey)
1 onion diced
2 slices of bread crumbled
1 egg
1 1/2 cups ketchup divided
1 tbls vinegar
1 tbls brown sugar packed

In a lg mixing bowl combine ground beef,onion,bread crumbs and egg. add one cup ketchup.Once all is moistened form a loaf shaped and place into a 9x9 baking dish coated with non stick cooking spray. Blend together remaining ketchup,brown sugar and vinegar until sugar is dissolved . pour mixture over top of meatloaf and bake uncovered for an hour at 375