Preheat the oven to 350 degrees Fahrenheit.
Cut the squash in half and scoop out the seeds. Place the squash cut side down onto a 9x13 or bigger baking pan, and add a little water to surround the squash (About 1/2 inch).
Bake the squash in the oven for about1 1/2 hours, or until fork tender.
Remove the squash from the oven and carefully remove the skin. Set it aside to cool partially.
Add 1 1/2 cups cooked squash into a blender, and blend until it is smooth.
Add the butter to a sauce pan, or pot and melt. Then add the remaining onion and garlic and cook for a few minutes until it is tender, and translucent.
Add the onion and garlic to the squash in the blender, and blend until smooth.
Add 2 cups of the tomatoes into the blender, and blend until it is smooth.
Return the vegetable mixture to the sauce pan. Stir in the chicken broth, heavy cream, and remaining herbs, and seasonings.
Stir the mixture until warm throughout, but don't bring it to a boil or the cream may curdle.
Scoop the soup into individual bowls and serve with your choice of garnishes.