Preheat oven to 450 F
Spread the tomatoes, onion and garlic in a baking pan. Season with salt, pepper, olive oil and basil. Place in the oven for 20 minutes.
Melt the butter in a large stock pot. Pour the chicken broth, water, and contents from the baking pan Into the large stock pot. Bring to a boil and then simmer for 15 minutes.
Mix the contents in the large stock pot with either a blender or hand blender. Simmer for another 5 minutes.
Server in a bowl.