Preheat your oven to 425 degrees Fahrenheit.
Cut the tomatoes into halves and place them on a baking tray.
Add the chopped onion and garlic cloves to the tray.
Drizzle everything with olive oil.
Sprinkle with salt, black pepper, sugar, and thyme.
Roast in the oven until the tomatoes are caramelized, approximately 30 minutes.
Transfer the roasted vegetables to a blender.
Puree until smooth.
If needed, work in batches, and be careful with hot ingredients.
While blending, gradually add the hot vegetable stock to the mixture.
Blend until you achieve the desired consistency.
You can adjust by adding more or less stock.
Pour the blended mixture into a pot over medium heat.
Stir in the cream and warm it through without boiling.