Preheat the oven to 400F. Toss the tomatoes with ¼ cup olive oil and season with salt and pepper. Layer on a baking sheet in a single layer. Roast in preheated oven for 45 minutes.
Meanwhile, in a large pot over medium heat, sauté the onions and garlic with 2 tablespoons of olive oil, butter, and red pepper flakes until the onion is translucent and starts to brown, about 10 minutes.
Add the canned plum tomatoes, chopped basil, thyme, and chicken stock. Add the oven roasted tomatoes, including the juices from the pan.
Bring the soup to a boil and then reduce heat and simmer for 40 minutes, uncovered.
Taste and add salt and pepper or more thyme or basil as needed.
Transfer the soup to a blender or large food processor and puree until smooth.
Serve with fresh grated parmesan cheese on top and a side of cheesy bread!
