Carefully remove the core from the cabbage. Place the whole cabbage in a large pot of boiling salted water and cook for 5-7 minutes, or until the leaves are pliable. Drain and let cool slightly. Gently peel off the leaves, reserving them for rolling.
In a large bowl, combine the ground beef, uncooked rice, chopped onion, minced garlic, 0.5 cup ketchup, salt, and pepper. Mix well.
Place about 1/3 cup of the meat mixture onto the stem end of each cabbage leaf. Fold in the sides of the leaf and roll up tightly.
In a separate bowl, whisk together the remaining 0.5 cup ketchup, brown sugar, lemon juice, tomato sauce, and diced tomatoes.
Pour half of the sauce mixture into the bottom of a 9x13 inch baking dish.
Arrange the rolled cabbage rolls seam-side down in the baking dish, on top of the sauce.
Pour the remaining sauce mixture over the cabbage rolls.
Cover the baking dish with foil and bake for 1 hour, or until the cabbage rolls are tender and the sauce is bubbly.
Let stand for 10 minutes before serving.
Notes
Serve hot with a side of mashed potatoes or a simple salad.