Bring a large pot of water to a boil. Submerge the whole cabbage head and blanch for 3–4 minutes until the outer leaves soften.
Remove cabbage with tongs. Let it cool, then peel off 10–12 large leaves. Trim the thick rib at the base of each leaf with a small knife.
Heat 2 tablespoons of olive oil in a skillet over medium heat. Sauté the chopped onion for 3 minutes until translucent. Add garlic and cook 1 more minute.
Add the cooked lentils and rice to the skillet. Sprinkle in cumin, smoked paprika, coriander, salt, and pepper. Stir well and cook for 2–3 minutes. Remove from heat and let cool slightly.
In the same skillet, heat 1 tablespoon olive oil. Sauté the diced onion until soft. Add garlic and cook 1 minute. Pour in crushed tomatoes, oregano, salt, pepper, and sugar if using. Simmer on low for 10 minutes.
Preheat oven to 375°F (190°C).
Lay a cabbage leaf flat. Place 2–3 tablespoons of filling near the base. Fold the sides inward and roll tightly from bottom to top. Repeat with remaining leaves and filling.
Spread a thin layer of tomato sauce on the bottom of a baking dish. Arrange rolls seam-side down. Pour remaining sauce over the top.
Cover tightly with aluminum foil. Bake for 30 minutes. Remove foil and bake an additional 10–15 minutes until tops are lightly browned.
Rest for a few minutes before serving. Garnish with fresh parsley or dill.