Add the crushed tomatoes, diced tomatoes, broth, onion, garlic, basil, oregano, salt, and pepper to your slow cooker. Stir well to combine.
Cover and cook on low for 360 minutes or on high for 240 minutes.
After cooking, use an immersion blender to purée the soup to your desired consistency.
Stir in the frozen cheese tortellini and heavy cream. Cook on high for an additional 20-30 minutes, or until the tortellini are tender.
Preheat your oven's broiler. Spread butter on one side of each slice of bread and place on a baking sheet, buttered side up. Sprinkle shredded cheddar cheese evenly over the bread slices.
Broil for 2-3 minutes, or until the cheese is melted and bubbly. Remove from the oven and cut into bite-sized squares.
Ladle the soup into bowls and serve hot with a generous portion of cheddar toast bites on the side or as a dunkable treat!