Melt 1 tablespoon butter in a large saucepan over medium heat. Add fennel, seeds, and scallions; saute 6 minutes. Add 1 1/2 cups water, 2 teaspoons brown sugar, and tomatoes; bring to a boil. Reduce heat to a simmer, and cook 5 minutes, stirring occasionally. Season with salt and pepper. Stir in 1/4 cup cream, if desired.