Roast the peppers on a baking sheet in a 425 deg oven for about 40 min, turning every 10 min. Remove from the oven, place in a bowl and cover. Allow to cool, then peel, seed and dice. Set aside.
Heat the oil over medium heat in a large, heavy soup pot and add the onion. Cook, stirring often, until onion is translucent, about 3 minutes.
Add the carrot and celery and a pinch of salt. Cook, stirring often, until the vegetables are tender and fragrant, about 5 more minutes.
Add the garlic, dried basil and cinnamon and cook, stirring, until fragrant, 30 seconds to a minute.
Add the tomato paste and tomatoes (with their liquid if using diced tomatoes). Cook over medium heat, stirring occasionally, about 10 minutes.
Add the diced roasted peppers, potatoes and vegetable broth. Bring to a boil, reduce the heat, cover and simmer 30 minutes, stirring from time to time.
Using a handheld immersion blender, purée the soup, or use a traditional blender and purée in batches, then return to the pot.
Season with freshly ground pepper, taste and adjust salt. Garnish with fresh basil.
Serve with garnish of choice such as: fresh basil or parsley, grated Parmesan cheese, croutons, a dollop of pesto, or a swirl of olive oil.
Notes
This will keep for about 3 days in the refrigerator and can be frozen.