Bring a large pot of unsalted water to the boil. Using a small sharp knife, carefully peel the skins off 5 of the onions, keeping them hinged at the bottom. Cut each onion with 1 slash lengthways, but just halfway through to the other side. This is to help the leaves loosen away during boiling. Boil until tender, about 15 minutes. Drain and cool a bit so you can handle them.
Peel and chop the remaining onion. Heat 3 tablespoons of the olive oil in a large non-stick frying pan. Add the chopped onion and sauté until softened and a bit golden. Add the minced beef and stir through, cooking until all the liquid has evaporated and the beef is cooked and golden brown. Season with salt and pepper, and stir in the parsley. Stir in half a cup of the tomatoes and cook for a couple of minutes. Remove from the heat.
Preheat the oven to 180°C (350°F/Gas 4). Have a large oven dish of about 34 x 24 cm (13½ x 9½ inches) ready. Sit at a table. Gently remove the onion leaves from the stems, carefully unfurling them so they don’t tear. You need each leaf opened out as far as possible. The outer ones will of course be larger. Put about a tablespoon of mince towards one end of a leaf and roll up neatly and tightly. Fill and roll all the leaves, no matter how small they are, just add less filling to the little ones. Sit them in the dish, all tightly next to each other like seals on a beach. You won’t be able to fill and roll the very inner leaves, but sit these in the dish as well.
Mix the remaining tomatoes and 4 tablespoons of olive oil with the lemon juice in a bowl and season with salt and pepper. Pour this mix over the onions and sprinkle a little salt over the onion tops sticking out above the sauce. Bake for about 1¼ hours, until roasty and the sauce is slightly thickened. Serve warm with bread. Even at room temperature these are great.