Cut any larger tomatoes in half. Cut the onion into wedges and peel the garlic. Arrange in a baking pan or casserole dish.
Drizzle over the olive oil, season with salt and pepper and sprinkle over the red pepper flakes if using.
Cook for 40 minutes or until the tomatoes have softened and are starting to blister.
Once cooked, transfer the contents of the baking pan to a bowl - including all the juices. To keep warm, transfer from the pan into a large pot, and simmer once blended.
Add the basil and vinegar. Use an immersion blender to blend the ingredients.
Add up to a cup of vegetable broth or boiling water to the soup until the texture is to your liking.
Check for seasoning then ladle into bowls.
Add a drizzle of heavy cream and some basil leaves for garnish.
Notes
You can use large or small tomatoes in any color.If you prefer a chunkier, thicker soup you may prefer not to add any water or broth at all and minimally blend.If you would like a creamier, smoother soup keep blending and adding liquid until the soup reaches the desired consistency.The red pepper flakes are optional and can be omitted if you don't want the heat. se smoked paprika instead or leave the spices out altogether.If you love garlic you can increase the quantity to 6-8 cloves.Store in an airtight container in the refrigerator for 4-5 days, or freeze for up to one year.