Preheat oven to 350°F (177°C)

Heat 2 tablespoons of the oil in a heavy skillet over medium heat. Add the onions and pepper and cook until soft, about 5 minutes. Add the garlic, cook another minute or two, stir in the Italian herbs, and remove heat.

In a small bowl, whisk the eggs well - season with salt and pepper, and whisk to combine.

Put the beef in a large bowl, add the egg mixture, add the remaining 2 tablespoons olive oil, the Worcestershire, 2 tablespoons of balsamic, and ½ cup of marinara sauce. Add the parmesan, mozzarella and bread crumbs, and onions, then mix it with your hands until just combined - do not over mix.

Lightly oil a 9 x 5 loaf pan and pack the meat mixture into it. Whisk the remaining tablespoon balsamic in the remaining ½ cup of marinara, and spread this evenly over the meatloaf.

Bake for about an hour or until cooked. Allow resting for about 5 minutes before serving.