In a Dutch oven, sauté the butter, onion and garlic until fragrant and the onions are slightly transparent.
Add in the tomatoes, tomato paste, hefty pinch of salt and pepper, and cayenne and let simmer for 10-15 minutes
Using either an immersion blender or by transferring to a blender, puree tomato mixture.
Return to the Dutch oven and finish with heavy cream, basil and parsley.
For the grilled cheese croutons, spread room temperature butter on one side of each slice of bread. Add equal parts cheddar and mozzarella cheese to 4 slices (about ½ inch thick), and top with other slice of bread.
Put butter side down on a medium-high heated non-stick skillet. Flip to the other side once the first side is medium-browned.
Once done cooking,Cut into 1 inch thick cubes and add as a topper to the soup.