Sauté leek in butter until tender and transparent . Add broth, tomato juice, and sugar, stirring well. Bring mixture to a boil ; reduce heat, and simmer 10 minutes.
Combine cornstarch, vinegar, and wine, mixing well; stir into tomato juice mixture . Cook, stirring constantly , until slightly thickened. Stir in chopped tomato, salt, and pepper. Serve hot; garnish with chopped green onion, if desired.