On a large baking sheet, spread out the quartered tomatoes, chopped onion, and whole garlic cloves. Drizzle with olive oil and sprinkle with salt and pepper.
Roast in the oven for about 25-30 minutes, or until the tomatoes are caramelized and the onions are tender.
Remove from the oven and let cool for a few minutes. Once cool enough to handle, squeeze the garlic from its skins and discard the skins.
In a large pot, combine the roasted tomatoes, onions, garlic, vegetable broth, dried basil, and dried oregano. Bring to a simmer over medium heat and cook for 10 minutes.
Using an immersion blender, blend the soup until smooth. If you don’t have an immersion blender, carefully transfer the soup to a blender in batches and blend until smooth.
Return the soup to the pot and stir in the heavy cream. Heat over low heat until warmed through. Adjust seasoning with more salt and pepper if needed.
Serve hot, garnished with fresh basil leaves on top.
Notes
For a vegan version, substitute heavy cream with coconut cream or a non-dairy alternative.