Get your oven ready! Preheat it to 425°F (220°C).
Wash and dry your tomatoes, then slice each in half. For bigger tomatoes, quarter them. Gently remove and discard the cores.
On a baking sheet, arrange the halved tomatoes, chopped yellow onion, and unpeeled garlic cloves. Drizzle generously with olive oil, then sprinkle with dried oregano, half of your salt, and half of the black pepper.
Gently toss everything together on the baking sheet to ensure an even coating. Roast in the preheated oven for 30-35 minutes, making sure to give them a stir halfway through for perfectly roasted veggies.
Once roasted, carefully remove the peels from the garlic cloves (they should be soft and easy to squeeze out). Transfer the peeled garlic, roasted tomatoes, onions, and any lovely pan juices into your blender or food processor.
Blend until super smooth and creamy. Then, pour this beautiful puree into a Dutch oven or a large pot and warm it over medium heat.
Stir in the vegetable broth, fresh basil, and the remaining salt and pepper. Let it gently simmer for 5 minutes, allowing the flavors to meld beautifully. Next, pour in the heavy cream and grated Parmesan cheese, and simmer for another 5 minutes until heated through and utterly delicious.
Serve warm in bowls, optionally garnished with a little extra fresh basil and a light drizzle of cream. Enjoy this comforting, healthy bisque!