In a medium pot, melt butter over medium-high heat, add onion and a pinch of salt, and cook until translucent. Add garlic and pinch of red pepper flakes, stir until fragrant.
Add can of whole peeled tomatoes, with all the juices, crushing each tomato over the pot, season with kosher salt and freshly ground black pepper. Add tomato paste and mix well to incorporate.
Add in vegetable broth, bring to a boil, and allow to simmer for 20-25 minutes. Using an immersion blender, blend soup until completely pureed. If you have fresh basil on hand, definitely add some in before blending.
Add in heavy cream, stir well to incorporate, and adjust seasonings as needed.
