Roast the Tomatoes
Preheat the oven to 450° F and line 2 baking sheets with parchment paper
Arrange the tomatoes on the baking sheets, in a single layer. Drizzle with olive oil and balsamic vinegar. Sprinkle the garlic, sugar, salt, and pepper over the tomatoes.
Roast for 25 to 30 minutes, until the tomatoes are concentrated and beginning to caramelize
Make the Soup
Heat the oil in a medium saucepan, add the onion and sauté, stirring often, for ~ 5 minutes, or until they're translucent.
Add the cumin and garlic, and sauté for an additional 2 minutes.
Add the stock, both roasted and canned tomatoes, sugar, red pepper flakes (if using), a ½ tsp of fine-grain sea salt, and a good grind of black pepper.
Bring to a gentle simmer and cook, stirring occasionally, for ~ 20 minutes, adding the bread halfway through.
Add the cilantro, and pulse the soup a few times (in batches) in your blender or food processor, to break down the tomatoes a bit (we like our soup on the coarse and chunky side)
(This soup should be pretty thick, but add a little water to thin it down if you prefer.)
Serve with a drizzle of oil and garnished with fresh cilantro.