Mighty Mexican Pizza

• 1 loaf bread dough (frozen white thawed)
• 120 ml taco sauce
• 120 gr seeded tomatoes (chopped)
• 110 gr exta beef (lean ground)
• 55 gr low-fat cheddar cheese (shredded)
• 45 ml nonfat sour cream (optional)
• 20 gr leaf lettuce (shredded)
• 16 gr onion (chopped)
• 16 gr green onions (sliced)
• 8 gr cornmeal