Place the cashews in a medium bowl and cover with water. Set aside for one hour.
Heat a large stockpot over medium heat and add the onions and garlic, stirring often.
Add the tomatoes, basil and salt, along with 3 c. water, cover, and bring to a boil.
Return to a simmer, and cook, covered, for one hour, stirring occasionally.
Make the cashew cream sauce: rinse and drain the cashews and place in a high powered blender with 1 cup of water. Blend until smooth.
Next, remove the soup from the heat. Using an immersion blender (or slowly, carefully, pour into a blender), blend the soup until creamy.
Pour in the cashew cream sauce, and heat through.