Preheat your oven to 400°F (200°C). Wash and cut the tomatoes into quarters. Toss with olive oil and salt, then spread on a baking sheet and roast for 30-35 minutes until caramelized.

In a large pot, heat olive oil over medium heat. Sauté diced onion for about 5 minutes until translucent, then add minced garlic and cook for 1 more minute.

Add the roasted tomatoes to the pot, along with the broth, dried basil, Italian seasoning, and sugar. Stir and simmer for 10 minutes.

Blend the soup until silky smooth using an immersion blender or a stand blender in batches.

Return the blended soup to the pot, stir in heavy cream, and gently heat for about 5 minutes without boiling.