Preheat oven to 450 degrees F. Lay the tomatoes on a baking sheet, cut side up. Drizzle with olive oil and season with salt and pepper. Roast for about 45 minutes, until tender and soft.
Heat the butter over medium heat in a heavy pot. Add the onions and cook until soft and translucent. Add the garlic and seasonings and cook for another minute.
Add the pumpkin, stir and add the broth. Bring to a simmer and simmer for 10 minutes.
Puree until smooth using either and immersion blender or regular blender.
Transfer to bowls and top with your favorite toppings.