Brush a 9 1/2 x 1 1/4-inch fluted tart pan with removable base with melted butter. Sift together the flour and salt into a large bowl, add the butter and, using a fast, light flicking action of the thumb across the tips of the fingers, rub into the flour until the mixture resembles fine bread crumbs. Make a well in the center and pour in the egg and 2 teaspoons water. Mix together to make a rough ball. Turn out onto a lightly floured surface and knead very gently for 20 seconds until just smooth, place in plastic wrap and chill for at least 20 minutes.

Roll out the pastry on a floured surface to a circle approximately 1/8-inch thick. Fold half the pastry over the rolling pin and lift into the pan. Push into the sides of the pan by using a small ball of lightly floured excess pastry. Trim off any excess pastry with a sharp knife or roll over the top of the pan with the rolling pin. Refrigerate for 30 minutes. Preheat the oven to 350F

Cut a circle of waxed paper 1-1/4 inches larger than the tart pan, crush it into a ball to soften, then open and lay inside the pastry shell so that it comes up the sides. Fill with pie weights or rice, then press down gently and bake for 10 minutes, or until firm. Remove the weights or rice and discard the paper, Return the pastry to the oven and continue to bake for 5 - 10 minutes, or until the pastry is dry. Remove and cool, Raise the oven temperature to 375F.

For the filling, heat the oil in a large saucepan. Add the onions and cook gently for 8 minutes, or until translucent. Raise the heat, add the sugar and cook for 5 - 10 minutes, or until the onions begin to caramelize. Next, pour in the wine and cook until the liquid has evaporated and the onions are soft. Season with salt and pepper. Remove from the pan and set aside.

In the pan, melt the butter, add the spinach and fry over high heat, stirring constantly, until the spinach is dry when pressed with the back of a spoon. (Wet spinach will make the quiche soggy.) Season with salt, pepper and the nutmeg, turn out onto a chopping board and chop finely.

In a saucepan, warm the cream and cheese gently, stirring, until the cheese melts, but does not boil. Season and cool before adding the eggs. Fill the pastry shell with the onion, then the spinach. Smooth the surface a little but do not pack down. Pour in the cream mixture and bake for 30 minutes, then lower the temperature to 325F and bake for 20 minutes to cook the center of the quiche. Cover with foil if it is getting too brown. Serve warm.