First dry the tomatoes: preheat the oven to 120°C/250°F/gas ½. Blanch the tomatoes in boiling water for 15 seconds, refresh in cold water and skin. Cut in half and scoop out the pulp and seeds. Lay the tomato halves cut side up on a lightly oiled baking tin. Sprinkle over the sugar and salt and put into the oven for 1–1½ hours, moving the outer halves to the inner area of the tray halfway through to ensure an even result. They should have shrunk with moisture loss, but not be as dry as a sun-dried tomato.
Make the pastry: put the flour, butter and a pinch of salt in a food processor and blitz to a crumb. While continuing to work, add an egg through the feeder tube, then add the iced water, a tablespoon at a time, until the pastry balls. Remove, cling-wrap, form into a ball then press into a 2 cm / ¾ inch thick disc and refrigerate for an hour.
Roll the chilled pastry out thinly and use to line a 25-cm / 10-inch tart pan. Return to the fridge to rest for at least an hour or overnight before baking.
When ready to make the tart: preheat the oven to 180°C/350°F/gas 4. Line the pastry shell with foil, then weight the top with beans or ceramic baking weights and bake blind for 15 minutes. Remove the weights and foil and continue baking until golden brown in the centre, about 10 minutes more.
Arrange the dried tomato halves to cover the base. In a large bowl, whisk the eggs then stir the cream followed by the Parmesan and season with salt, pepper and grated nutmeg to taste. Pour over the tomatoes and return to the oven, immediately lowering the temperature to 150°C/300°F/gas 2, and bake for 25–30 minutes or until just set.