Pour cashews and 1 cup of water into a blender to soak while you start the soup.
Set stockpot over medium heat and add oil. Add onions and season with salt. Cook until onions are softened. Add another drizzle of olive oil and tomato paste. Deglaze the pot with 1 cup of water. Add the whole peeled tomatoes and their juices. Season with salt.
Simmer for about 40 minutes. Turn off heat and use an immersion blender to blend until smooth.
Blend the cashews and water until smooth, then pour into the soup. Blend with the immersion blender again. Taste and adjust seasoning if needed. Add more water if you want a thinner soup.
Recipe by the minimalist table at https://www.daraboxer.com/theminimalisttable/the-creamiest-tomato-soup-without-cream/