Preheat oven to 425°F. Place bread shell on a large pizza pan or baking sheet lined with parchment paper; set aside. In a small bowl whisk together tomato paste and the reserved cooking juices from the Wine-Braised Beef Brisket. Chop the reserved beef.
Spread tomato paste mixture over bread shell. Top with beef, mushrooms, sweet pepper and cheeses. Bake 12 to 15 minutes or until heated through and cheese is melted. Cut into 6 wedges to serve.