Remove core from cabbage. In large pot of boiling salted water, cover and cook cabbage for 8 to 10 minutes or until leaves are softened and easy to remove. Chill in cold water. Carefully remove 12 leaves, returning cabbage to pan for 2 to 3 minutes if leaves become difficult to remove. Drain on towels. Pare off coarse veins; set leaves aside.

In saucepan, heat oil over medium heat; cook onion, garlic, marjoram, thyme, and caraway seeds (if using) for 5 minutes or until softened. Stir in rice. Add stock and bring to boil; reduce heat,, cover and simmer for 20 minutes or until rice is tender. Stir in carrot, zucchini, salt and pepper.

Let cool to room temperature. Stir in egg. Spoon about 1/3 cup (75 mL) onto each leaf just above stem. Fold bottom and sides over filling; roll up.

Line 13- x 9-inch (3 L) baking dish with half of the sauerkraut. Arrange cabbage rolls on top; cover with remaining sauerkraut. Whisk tomato paste into tomato juice; pour over rolls. Cover with foil; bake in 350°F (180°C) oven for 2 hours or until tender.