Preheat oven to 325°F. In a large glass baking dish, or a parchment line baking, add the tomatoes, optional red bell pepper, onion, carrot and garlic cloves. Drizzle with the grapeseed oil, and lightly season with salt. Stir everything together. Bake in oven for 1 hour and 30 minutes. Veggies should be lightly browned on top.
Heat a large pot or Dutch oven over heat. Add the roasted vegetables, tomato paste, sea salt, black pepper and oregano. Stir together, and bring to a simmer. Cover and let simmer for 20 minutes.
Add contents of the pot, along with the basil leaves to a blender, and blend until smooth. I use an immersion hand mixer, which can also be used without having to remove the contents from the pot. Just be sure to add the basil before doing so.
Return soup to simmer, and stir in heavy cream and optional Parmesan cheese. Remove from heat, and serve warm.
