Drain the tomatoes in a colander. Peel and dice onions and garlic. Heat the oil in a large saucepan, briefly sauté the onion and garlic cubes. Stir in the risotto rice with a wooden spoon or spatula and sweat briefly until translucent. Gradually stir the tomato juice into the risotto, cook on a low flame for about 20 minutes. If the risotto needs more liquid, stir in the vegetable stock in sips.
When the cooking time is over, add the tomato pieces to the risotto, stir and allow to warm up. Season to taste with sugar, salt and pepper. Sprinkle tomato risotto with parmesan and parsley before serving.