Remove dark outer leaves from cabbage.
Core cabbage.
Place cabbage in a large bowl of hot water until leaves are easily separated.
Remove 8 large leaves, reserve remaining cabbage for other uses.
Cook leaves in boiling water 6 to 8 minutes or just until tender.
Drain and set aside.
Coat a medium skillet with cooking spray; place over medium heat until hot.
Add onion, and saute until tender.
Combine onion, rice, sunflower kernels, and cheese in a medium bowl; mix well.
Place 1/3, cup rice mixture in center of each cabbage leaf; fold sides in over rice mixture, and roll up each leaf.
Secure each cabbage roll with a wooden pick.
Place cabbage rolls in a large skillet.
Combine tomato sauce, Worcestershire souce, and pepper in a small bowl; mix well.
Pour over cabbage rolls in skillet.
Bring to a boil.
Cover, reduce heat, and simmer 15 minutes.
Remove cabbage rolls to a serving plate, and serve immediately.