Core the cabbage and place in a large pot of water.  Bring to a boil, then simmer, covered, for 15 minutes until cabbage is wilted.  Run under cold water and drain.  Line a large baking pan (13x19x2) with sliced onions.  In a medium bowl, combine ground turkey, onion, garlic, rice, salt, and pepper.  Assemble by putting about 3-4 tbsp. meat mixture onto each cabbage leaf.  Roll up, then tuck ends under.  Arrange seam side down on top of the onions.  In a medium bowl, mix together ketchup, tomato juice, brown sugar, and lemon juice.  Pour sauce over cabbage rolls.  Cover and bake at 350 for 1 1/2 to 2 hours.