In a Dutch oven over medium heat, melt the butter. Add the onions and celery and cook until tender, about 5 minutes. Add the tomatoes, red peppers, Italian seasoning, red pepper flakes and bay leaf. Stir to combine and sprinkle with the flour. Cook until the flour starts to brown, about 3 minutes.
Meanwhile, combine the vegetable stock, white wine and reserved juice from the canned tomatoes in a saucepan and bring up to a simmer. Slowly pour the hot liquid into the vegetable mixture, stirring the entire time. Cover and cook on low for 20 to 25 minutes. Remove the bay leaf.
Using a hand mixer or blender, blend the soup until smooth and return it to low heat in the Dutch oven. Let the mixture reduce by one-quarter, 7 to 10 minutes, and then stir in the cream. Season with salt and pepper to taste.
When blending hot liquid, first let it cool for five minutes or so, then transfer it to a blender, filling only halfway. Put the lid on, leaving one corner open. Cover the lid with a kitchen towel to catch splatters, and pulse until smooth.