Preheat oven to 450 degrees.
Strain the diced tomatoes, reserving the juice and spread on a baking sheet (I sprayed mine with Pam just to be sure it did not stick). Add to the tomatoes the carrots and garlic. Salt and Pepper to taste and drizzle with about 1 1/2 T olive oil. Stir well. Place in oven and roast for about 35 to 45 minutes (ovens do vary, mine is really old so yours may not take quite that long).
As the tomato mixture is roasting, heat remaining olive oil and 1 T Butter in a stockpot. Saute onions on medium heat for about 10 minutes or until they start to turn a light brown. Set aside to cool until the tomatoes are ready to use.
When the tomatoes are ready add them to the stockpot with the onions. Add the reserved juice, tomato sauce, the chicken broth, bay leaf and butter and red pepper flakes. Simmer for about 20 minutes on low. When done let cool for a few minutes. Remove the bay leaf.
Using a blender or a handheld immersion blender, blend until your desired consistency, we like ours just a little chunky. When done add back to the stockpot and add the cream and basil and heat on low until all of the cream is incorporated.
Serve topped with parmesan cheese if using.