Arrange tomatoes, cut side up in one layer on a large baking sheet. Scatter garlic around tomatoes. Drizzle tomatoes with oil and sprinkle with ½ teaspoon of salt and a few grinds of pepper.
Roast until tomatoes are browned around the edges but still juicy, about 1 hour. Allow to cool, then peel garlic. Leave the oven on and bake the Crispy Manchego Wafers, recipe below.
Melt butter in a heavy 6-8 quart saucepan over medium heat. Add onion, oregano, and sugar and cook, stirring frequently, until onion is softened, about 5 minutes. Add tomatoes, garlic, and stock, bring to a simmer, and simmer, covered for 20 minutes to allow flavors to blend.
Remove from heat and use an immersion blender to puree the soup. Return to low heat, stir in cream and salt and pepper to taste. Simmer for 2 minutes. Divide among bowls and serve immediately.
Shown served with Crispy Manchego Wafers (recipe follows)
*I substituted vegetable broth for chicken for a vegetarian soup, also used fresh red and yellow tomatoes from the garden and cut the amount of onion, sugar and butter in half. Yellow tomatoes tend to be sweeter and less acidic, so the combination gave the soup more of an orange color and rich, mellow flavor.