Preheat the oven to 200°C/400°F (180°C fan) and line a large tray with baking paper.
Cut the tomatoes in half and the onion into quarters and place on a baking tray along with the garlic. There's no need to peel the garlic as this can be roasted whole then squeezed out of its skin when cooked.
Drizzle with olive oil and sprinkle salt over the top and bake in the oven for 40-50 minutes until soft and starting to caramelize. Keep an eye on it as they can burn easily.
Once ready, squeeze the garlic out of its skin and place into the Thermomix bowl along with the tomatoes, onion, stock and basil.
Blend for 30-60 sec/speed 7. Check for consistency, if it's a little thick, add a little more water and blend again. Season to taste. If you like it thick and chunky, blend for less time.
If you're serving the soup straight away, heat it up in the Thermomix for 5 mins/100℃/speed 1 until piping hot.
Serve with fresh crusty bread and a sprinkling of Parmesan and fresh basil on top.
Notes
Roma tomatoes: Roma tomatoes which are great for cooking with or you could also use truss or gourmet tomatoes.Stock: I like to use stock cubes. You could also use Thermomix vegetable stock concentrate or stock from a carton. Just don't add more than 250 ml so it's not too runny.To freeze: Allow the soup to cool completely before freezing. Ladle into a freezer proof container or bag but don't overfill as it will expand once frozen. Consume within 3 months.