Preheat oven to 425 degrees F.
Place tomatoes and garlic cloves on a baking tray, drizzle with 2 tablespoons of olive oil, season with salt, pepper, and dried Italian herbs, roast for about 25 minutes, or until the tomatoes are soft and charred on the tops.
Remove tray from oven and transfer the tomatoes and garlic to the slow cooker with all the juices from roasting.
Add the diced onion, red bell pepper, season with dried basil, red pepper flakes, salt, and pepper.
Add the tomato paste and broth, stir to combine.
Cover and cook on High for 3 hours or on Low for 6 hours.
When there are 30 minutes of cooking remaining, stir in the heavy cream, cover and cook for 30 minutes.
Using an immersion blender or a Vitamix, puree the mixture until it’s very smooth. I transferred the soup in two batches into the blender to puree it, but if you use an immersion blender you can puree the soup directly in the crockpot.
Serve garnished with grated parmesan cheese and fresh basil leaves.
Store in the fridge for up to 3-4 days or freeze for later.
