For the cabbage rolls:
1) Bring a large pot of salted water to a boil. Add the cabbage leaves and cook, until tender, about 4 minutes. Drain the leaves into a colander in the sink and refresh under cold running water. Set aside.
2) In a large bowl, place the beef, rice, sour cream, and 2 teaspoons salt.
3) Heat the butter in a medium skillet over medium heat. Add the onion and garlic and cook, stirring, until soft, about 7 minutes. Stir in the paprika and allspice and cook, stirring, until fragrant, about 2 minutes more. Add the onion mixture to the beef mixture, and mix until well combined. Season with pepper to taste.
4) Lay the cabbage leaves on a work surface and blot dry with paper towels. Slice off the ridged part of the thick rib at the bottom each leaf, creating a level surface over the leaves. Place about 1/2 cup of the beef mixture in the bottom center of each roll. Roll the bottom of a leaf over the beef mixture, fold in the sides, and continue rolling forward until completely closed. Repeat with the remaining leafs.
Arrange the rolls seam side-down in a 23x33x5cm oval gratin dish.
5) Preheat the oven to 190C/Gas 5.
For the tomato sauce:
1) In a medium saucepan, combine the tomatoes, broth, salt, and bay leaf. Bring to a boil and season with pepper to taste. Pour over the cabbage rolls and cover the baking dish tightly with foil. Bake for 1 hour.
2) Remove the foil from the baking dish and continue cooking, basting occasionally, until lightly browned and cooked through, about 30 minutes more. Serve in the gratin dish.