Melt butter in a large pot over medium heat. Add thyme, onion, and
garlic. Cook until onion is completely soft and translucent, 10–12
minutes. Increase heat to medium-high; add tomato paste. Continue
cooking, stirring often, for about 6 more minutes.
Add tomatoes and 8 cups water to pot. Bring to a simmer for about, 50
minutes. Remove soup from heat; let cool slightly.
Working in small batches, purée soup in a blender until smooth. You can also use an Immersion blender right in the pot if you have one!
Stir in ¼ cup cream. Simmer soup until flavors meld, about 15 more minutes. Season to taste with salt, pepper. Add more cream, if desired for extra creamy texture.