Roasted Plum Tomato Jam: Heat oven to 300°F. Combine all ingredients in a large bowl. Toss the tomatoes with the other ingredients. Place tomatoes cut side down on a sheet pan.
Bake tomatoes for two hours or until slightly browned and shriveled. Allow them to cool down until you can handle them. Remove skins. Place the tomatoes in a ceramic or stainless steel pot and mash. Now Cook on low heat for about 30 minutes or until the mixture becomes jam-like. You can do this step up to a week in advance.
Grilled Cheddar Cheese Croutons: 2 slices of cheese between 2 slices of white bread. Spread tomato jam on both. Butter both sides of each sandwich. Toast the nonstick skillet on medium heat. Add a little butter.
Toast the grilled cheese sandwiches until golden brown on both sides and the cheese has melted, about 1-2 minutes on each side. Let the sandwiches cool in the pans for about 1-2 minutes. Cut into 1-inch croutons. Serve soup in bowls. Top with a few grilled cheese croutons.