MAKE THE CRUST:
- In a food processor fitted with a steel blade, or in a large bowl, pulse or mix together flour, sugar and salt. In a measuring cup, lightly beat the egg, then add just enough cream to get to ⅓ cup. Lightly whisk the egg and cream together.
- Add butter to flour mixture and pulse or use a pastry cutter or your fingers to break up the butter. If using a food processor, do not over-process; you need chickpea-size chunks of butter. Drizzle the egg mixture (up to ¼ cup) over the dough and pulse or stir until it just starts to come together but is still mostly large crumbs. Mix in lemon juice and zest if using.
- Put dough on lightly floured counter and pat it together to make one uniform piece. Flatten into a disk, wrap in plastic and chill for 2 hours, or up to 3 days.
- Heat the oven to 400 degrees. Roll the dough out to a 12-inch round (it can be ragged). Transfer to a rimmed baking sheet lined with parchment paper and chill while preparing the filling.
MAKE THE FILLING:
- Toss together fruit, all but a tablespoon of sugar, the salt, the lemon juice and zest, and the cornstarch. Use more cornstarch for juicy stone fruit and less for blueberries, raspberries and figs. Pile fruit on the dough circle, leaving a 1 ½-inch border. Gently fold the pastry over the fruit, pleating to hold it in (sloppy is fine). Brush pastry generously with leftover egg and cream mixture. Sprinkle remaining sugar on the crust.
- Bake for 35 to 45 minutes, until the filling bubbles up vigorously and the crust is golden. Cool for at least 20 minutes on wire rack. Serve warm or at room temperature.
Drain the liquid from the fruit (peaches) after adding the sugar, cornstarch and lemon juice and cook it briefly to let it thicken. Then poured the thickened sauce back over the fruit after piling it in the dough. Much less leakage and better flavor than just leaving the juice out.