Bring a large pot of salted water to a boil. Carefully remove the core from the cabbage and place the whole head in the boiling water for about 5 minutes, or until the outer leaves are tender. Gently peel off the softened leaves and set them aside to cool.
In a skillet, heat the olive oil over medium heat. Sauté the chopped onion and garlic until softened, about 5 minutes. Add the ground beef, cooking until browned. Drain excess fat if necessary.
In a mixing bowl, combine the cooked meat mixture with the rice, paprika, salt, black pepper, and fresh parsley. Mix well to combine.
Preheat your oven to 350°F (175°C).
Take one cabbage leaf at a time and place about 2-3 tablespoons of the filling at the base of the leaf. Fold in the sides and roll it up tightly to enclose the filling. Repeat with the remaining leaves and filling.
In a baking dish, spread a thin layer of tomato sauce on the bottom. Arrange the stuffed cabbage rolls seam-side down in the dish. Pour the remaining tomato sauce over the top of the rolls, and sprinkle with dried thyme if desired.
Cover the baking dish with aluminum foil and bake in the preheated oven for 45 minutes. Remove the foil and bake for an additional 15 minutes to allow the sauce to thicken slightly.
Once cooked, remove from the oven and let cool for a few minutes before serving. Drizzle with a little lemon juice for added flavor if desired.