Carefully slice the tops off of the tomatoes and peppers and set them aside. Hollow out the peppers and discard the middles. Use a knife/spoon to scoop out the tomato flesh and put this straight into the bowl of a food processor.
Add 3 tablespoons of olive oil, the tomato puree, 3 cloves of garlic, 1 teaspoon of salt, white pepper, and sugar to the food processor with the tomato flesh. Blitz until smooth.
Pour the tomato sauce into the bottom of a large roasting pan and place the hollowed out peppers and tomatoes on top.
Heat the remaining 2 tablespoons of olive oil in a large, high-sided frying pan. Fry the onion, zucchini and carrot on a medium setting until softened — about 10 minutes. Then add the remaining 2 cloves of crushed garlic and cook for another minute, stirring constantly.
Add the ground beef and turn up the heat to high. Break it apart with a wooden spoon as it cooks. Keep going until it's completely cooked through and slightly browned.
Add the rice, oregano, canned tomatoes, and vegetable stock. Stir well and once boiling, reduce the heat to a simmer and leave to cook for 10 minutes. While the filling cooks, preheat the oven to 400 F.
Stir through the chopped parsley and some salt and pepper to taste, if desired.
Spoon the filling mixture into the prepared peppers and tomatoes, then place the tops back on.
Cover the roasting tray with foil and bake for 40 minutes. Then remove the foil and bake for another 40 minutes.
Serve with the tomato sauce spooned over the top of the peppers and tomatoes.