Lightly grease a baking dish that is large enough to hold all ingredients.
Place the tomatoes, onion, garlic and thyme into the baking dish, drizzle with olive oil and season lightly with salt, pepper and sugar.
Allow the tomato mixture to cool a little and then carefully pour it into a blender and process until smooth and creamy.
Check seasoning, adjusting if necessary.
If you do not have sour cream and/or basil pesto, a simple drizzle of extra virgin olive oil would also be the perfect finish for this delicious soup.