Place the tomatoes, onion nd garlic on a sheet pan and coat with the olive oil. Sprinkle with the salt and pepper and place in a 400 degree oven for 30-40 minutes, or until the tomatoes begin to char around the edges.
Remove the garlic and scrape the contents of the sheet pan into a large pot. Squeeze the garlic out of its peel and into the pot with the tomatoes. Add enough chicken broth to cover the tomatoes and bring up to a simmer. Add in half of the basil, then using a stick blender or a food processor, blend the soup into a puree. Return the soup to the pot and taste, add sugar if needed. Ladle into bowls, top with a drizzle of heavy cream and a sprinkle of basil. Serve!