1. Place the cashews in a container and pour over enough cold water to completely submerge. Let soak for at least one hour at room temperature.
2. Preheat the oven to 200 degrees Celsius (400 degrees Fahrenheit)/Gas 6.
3. Drizzle olive oil into a medium roasting pan.
4. Pour the canned tomatoes out onto the prepared roasting pan (with all the juices) and break apart with your hands. Note: be careful as they will splash your clothes – I recommend an apron or an old t-shirt for this job.
5. Scatter the tomatoes with the garlic and season with salt. Bake in the preheated oven for 40 minutes until bubbling and the juices have slightly reduced but are still plentiful.
6. Meanwhile, in a large saucepan over a medium heat, warm enough olive oil to cover the base. Add the onion and cook, stirring occasionally, for about 10 minutes until softened.
7. Add the tomato purée/paste and cook for two more minutes. Pour in the vegetable stock/broth and roasted tomatoes (along with the garlic) and simmer for about 10–15 minutes. Remove from the heat.
8. Blend the soup with a stick blender or in batches in a food processor until smooth.
9. Drain the soaked cashews and blend together with a fresh 120 ml/half cup of water with a stick blender or in a food processor until creamy.
10. Portion the soup into bowls and swirl in a little cashew cream to each. Serve with plenty of freshly ground black pepper and [when making year-round] nice bread on the side for dipping.