Preheat oven to 400 degrees Fahrenheit.

Slice tomatoes in half lengthwise and place cut-side up on a large rimmed baking sheet. Sprinkle with salt and pepper and drizzle with three tablespoons olive oil. Roast uncovered until tomatoes are nicely browned, 45 to 50 minutes, stirring occasionally.

Meanwhile, sauté garlic and onions in one tablespoon oil in a large pot until translucent.

Add roasted tomatoes, canned tomatoes, tomato paste, thyme, pepper flakes, sugar and water to pot and bring to a boil.

Cover and simmer on low heat for 10 to 15 minutes, stirring occasionally.

Remove from heat, stir in basil and let cool slightly. Purée using an immersion blender until smooth. (You can also pour the cooled soup into a blender and purée it.) Serve hot or cold.

SERVING SUGGESTION: Slice a baguette into thin slices, brush lightly with olive oil and top with grated Cheddar cheese. Toast or broil until golden. Place a slice or two (depending on size) in each bowl of soup just before serving.