Lay out tomatoes, onions and garlic on a baking sheet. Drizzle with olive oil, then sprinkle with salt and pepper.
Roast on 375 F for an hour, or longer if it looks like they need to be roastier.
Transfer the veggies into a pot on medium heat. Add the basil, chili flakes, and stock.
Bring to a boil, then simmer for 30 minutes.
Use an immersion blender to blend it up into soupy goodness.
Make your grilled cheese! You know how to do this. I like to use margarine on the bread on the pan side because it spreads nicer.
Cut up the grilled cheese and throw it in your soup when serving.