01 - Preheat the oven to 400°F.
02 - Cut the top off the garlic head to expose the cloves, drizzle with 1 teaspoon olive oil, wrap in foil, and place on a baking sheet.
03 - Place tomatoes cut side up and chopped onions on the same baking sheet, drizzle with remaining olive oil, and season with salt and black pepper.
04 - Roast for 30 to 35 minutes until tomatoes are soft and caramelized and garlic is golden.
05 - Toss bread cubes with olive oil, oregano, and salt; spread on a separate baking sheet and bake for 10 to 15 minutes, stirring once, until golden and crisp.
06 - Squeeze roasted garlic cloves out of their skins once cooled slightly.
07 - In a large pot, combine the roasted tomatoes, onions, garlic, vegetable broth, fresh basil, and sugar if using.
08 - Bring the mixture to a simmer over medium heat and cook for 10 minutes.
09 - Use an immersion blender or blend in batches until smooth, then return to the pot and stir in cream if desired; adjust seasoning with salt and pepper.
10 - Ladle soup into bowls, garnish with croutons and fresh basil leaves.