In a large heavy pot, add the olive oil, onion, garlic and salt. Bring to medium heat and cook until the onions have softened, 7 minutes. Add the tomato paste and stir to combine.
Pour in the canned tomatoes and broth and bring to a gentle simmer. Cook, with the lid off, for 10 minutes.
Ladle the soup into a high-speed and add the cashews and maple syrup. Blend (first on low and increase speed to high), for 2 minutes or until smooth and creamy. Stop to add the fresh basil leaves, and pulse if you prefer the leaves to be chunky, or blend if you prefer a smooth puree. Pour the soup into bowls and serve.
Store recipe in an air-tight container in the refrigerator for up to 1 week. It's recommended to blend on low first and increase speed to high. Otherwise the heat of the soup can cause a soup explosion when turning directly on high speed. (I speak from experience!).If you prefer to make this recipes sugar-free, forgo the maple syrup. It helps cut acidity, but is not necessary. Nutritional information is a rough estimate.