Heat the oven to 375F while you prepare the meatloaf mixture.
Combine ground beef, ground pork, onions, egg, tomatoes and breadcrumbs or oats, sugar, salt, and pepper in a large bowl. Mix all the ingredients until well blended. If necessary, use hands to make sure all ingredients are mixed well.
Transfer your meatloaf mixture into a bread pan or baking dish to shape like a loaf. Rub a little cool water on the top of the loaf and bake for 50 min. to 1 hour. Meatloaf is ready when it reaches an internal temperature of 170 F. Pork meatloaf is ready at 185F.