Toss tomatoes & quartered onions In olive oil and spread in one layer over a baking sheet ( you will probably need two)
Cut the top off of a head of garlic, drizzle with a little of the oil, and put it onto one of the baking sheets
Roast everything for about 30 minutes
Put vegetable stock, canned tomatoes, roasted tomatoes and onions, along with their juices, in a large pot
Squeeze out the roasted garlic into the soup
Use an immersion blender to puree right in the pot, or, transfer in batches to a blender or food processor, remembering to open the steam vent.
Bring to a boil, then reduce heat and simmer for 10-15 minutes
Add chopped fresh basil, and salt and pepper to taste. Garnish with more fresh basil.
Most commercial stocks, including vegetable stocks are very high in sodium, so this recipe uses a low sodium stock, and you can also find no salt added stocks if you want even less. Canned tomatoes are also available in "no salt added" versions.