Preheat the oven to 425°F or 220°C, cut the peppers in half, and remove the stems, seeds, and membranes.
Arrange the peppers cut-side down on a lined baking sheet and roast for 20 to 25 minutes until soft and lightly charred.
Heat the olive oil in a large pot, add the onion, and cook for about 4 minutes before stirring in the garlic.
Add the roasted peppers, tomatoes, vegetable broth, smoked paprika, basil, salt, and black pepper.
Bring the soup to a gentle boil, reduce the heat, and simmer for 12 to 15 minutes.
Blend the mixture carefully until it becomes smooth and velvety.
Stir in the low-fat milk and balsamic vinegar, then warm the soup gently without boiling.
