Add 3 lbs fresh tomatoes, halved and quartered, to the slow cooker. Then, include 1 large onion, roughly chopped, and 6 cloves of garlic, peeled and chopped.
Season the mixture with 1 tsp salt and 1 tsp black pepper. Gently stir everything to ensure the ingredients are well combined.
Cover the slow cooker and set it to cook on low for 6-8 hours or until the vegetables are completely soft.
Once cooked, use an immersion blender to blend the soup until smooth. If you don't have an immersion blender, you can transfer the mixture in batches to a standard blender. Be cautious with hot liquids!
After blending, return the soup to the slow cooker if needed, and stir in 1/3 cup heavy cream. Mix well until the cream is fully incorporated.
To serve, ladle the soup into bowls and garnish with freshly chopped parsley, extra black pepper, and more cream if desired.