Prepare the Cabbage: Bring a large pot of water to a boil. Carefully blanch the cabbage leaves for 2-3 minutes until soft and pliable. Drain and pat dry with a kitchen towel.

Cook the Filling: Heat olive oil in a skillet over medium heat. Sauté onions, garlic, carrot, zucchini, and bell pepper until softened, about 5-7 minutes. Stir in cooked rice or quinoa, thyme, paprika, salt, and pepper. Cook for 2 more minutes, then set aside to cool slightly.

Roll the Cabbage Leaves: Lay a cabbage leaf flat and place 2-3 tablespoons of the vegetable filling in the center. Fold the sides over the filling, then roll tightly. Repeat with all leaves.

Prepare the Sauce: Heat olive oil in a saucepan over medium heat. Sauté onions and garlic until fragrant. Add crushed tomatoes, oregano, sugar (if using), salt, and pepper. Simmer for 10-15 minutes.

Cook the Rolls: Preheat the oven to 350°F (175°C). Spread a thin layer of tomato sauce on the bottom of a baking dish. Arrange cabbage rolls seam-side down, then pour the remaining tomato sauce over them. Cover with foil and bake for 30-35 minutes until heated through.

Serve: Garnish with fresh parsley and serve hot with crusty bread or mashed potatoes.