Heat a dutch oven or heavy bottomed pot over medium heat. Once hot, add the olive oil, onion, and garlic. Sauté the onions and garlic for 4-5 minutes until the onions soften and become translucent.
Next, add the roasted diced tomatoes, crushed tomatoes, chicken broth, balsamic vinegar, salt, and red pepper flakes to the pot. Simmer the soup for 30 minutes.
After the soup has simmered, transfer it to a blender and blend until smooth. Then, add the fresh basil and blend again. Transfer the soup back to your pot and add in the coconut milk. Simmer for 10 more minutes.