Remove 8 outer leaves from cabbage; place leaves in a large stockpot (reserve remaining cabbage for another use). Add enough water to cover leaves; set pot over high heat. Bring water to a boil; boil until leaves are pliable and soft, about 10 minutes. Drain; when leaves are cool enough to handle, cut off thickest part of vein from bottom of leaves, leaving leaves intact.

Meanwhile, in a large bowl, combine turkey, onion, rice, egg, garlic powder, cinnamon, salt and black pepper; mix well.

Place a small amount of turkey mixture (enough to fit in the palm of your hand) onto center of each leaf. Fold in sides of leaves and then roll up tightly from one end to other, making sure filling is fully covered by leaf. 

Pour a small amount of tomatoes into stockpot so a thin layer covers bottom of pot. Place cabbage rolls in pot, packing them tightly to prevent opening during cooking; pour in remaining tomatoes and broth. Set pot over medium-high heat and bring to a simmer; reduce heat to low, cover pot and simmer 45 minutes more. Remove from heat and serve hot. Yields 2 stuffed leaves and about 1/4 cup of sauce per serving.