Measure 1 liter of vegetable stock. Blend half with 400g of canned chopped tomatoes until smooth. Pour into a saucepan with the remaining stock and keep at a gentle simmer.
Heat 1 tablespoon of olive oil and 1 tablespoon of butter in a wide pan. Add 1 onion, finely chopped; cook for 6-8 minutes until soft.
Add 2 garlic cloves, chopped, and the finely chopped leaves of 1 rosemary sprig. Stir for 1 minute, then add 250g of risotto rice and stir for another 1 minute.
Add the hot tomato stock gradually, stirring often and letting each addition absorb. Once half is used, add 300g of cherry tomatoes, halved. Continue until the rice is tender and creamy, about 20-25 minutes in total.
Rest covered for 1 minute. Stir in torn basil and season with salt and black pepper. Top with 4 tablespoons of grated Parmesan.
