01 - Preheat oven to 400°F.
02 - Cut the top off the garlic head to expose cloves, drizzle with 1 tsp olive oil, wrap in foil, and place on baking sheet.
03 - Arrange tomatoes cut side up and chopped onion on the baking sheet, drizzle with remaining olive oil, and season with salt and pepper.
04 - Roast garlic, tomatoes, and onion 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 separate baking sheet and bake 10 to 15 minutes, stirring once, until golden and crisp.
06 - Squeeze roasted garlic cloves out of skins once roasting is complete.
07 - In a large pot, combine roasted tomatoes, onions, garlic, vegetable broth, basil leaves, and sugar if using.
08 - Bring mixture to a simmer over medium heat and cook for 10 minutes.
09 - Purée soup using immersion blender or in batches in a countertop blender until smooth; return to pot.
10 - Stir in cream if desired and adjust seasoning with salt and pepper.
11 - Ladle soup into bowls, garnish with croutons and fresh basil.