Peel the onions and carefully cut off the tops. Use a spoon or a melon baller to scoop out the centers, leaving the outer layers intact to form cups. Blanch the onions in boiling water for about 5 minutes to soften them slightly. Drain and set aside.
In a large mixing bowl, combine the ground beef or lamb, uncooked rice, finely chopped onion, minced garlic, chopped parsley, dill, and mint (if using).
Add ground black pepper, salt, paprika, and drizzle in the olive oil. Mix everything thoroughly until well combined.
Stuff each prepared onion with the filling mixture, packing it in tightly.
Place the stuffed onions upright in a large pot or baking dish.
Drizzle the stuffed onions with olive oil.
Combine the tomato sauce, beef or vegetable broth, and lemon juice in a bowl. Pour this mixture over the stuffed onions. The liquid should almost cover the onions; add more broth or water if needed.
Place a heatproof plate on top of the onions to keep them submerged during cooking.
Bring the pot or dish to a gentle simmer over medium heat.
Reduce the heat to low, cover, and simmer for about 45-60 minutes, or until the rice and meat are cooked through and the onions are tender.
Remove the stuffed onions from the pot or dish and let them cool slightly.
Enjoy your meal!