For the crust, in a large bowl, combine the flour and salt. Add the butter and use your hands or a pastry blender to work the butter into the flour until it resembles coarse crumbs. Add the cold water and stir with a rubber spatula until it comes together to form a rough dough. Form into a disc, wrap in plastic wrap and chill for at least 30 minutes to 1 hour.
To make the cream filling, in a large bowl, cream together the cream cheese and sugar until fluffy. Stir in the egg, vanilla, lemon and flour until well combined. Chill until ready to use.
To make the streusel topping, in a bowl, stir together the flour, sugar, cinnamon, nutmeg and salt. Add the butter and rub with your fingers until it resembles coarse crumbs. Set aside.
Preheat the oven to 375°F. Line a baking sheet with parchment paper and set aside.
Once the dough has chilled, transfer to a lightly floured work surface and roll out into a large circle about 1/4-inch thick. Transfer to the prepared baking sheet.
Add the cream filling to the center of the rolled out dough and spread out leaving a 3-inch border along the edge. Top the cream with peach slices as you'd like. You can fan them out slightly overlapping or you can add them haphazardly. Sprinkle the top evenly with the streusel.
Gently fold the edges of the dough over the filling, overlapping the dough as you go along. Brush the edges with egg wash and sprinkle with turbinado sugar if using.
Bake until deeply golden brown, for 40 to 45 minutes. Remove from the oven and allow to cool for 10 minutes before slicing and serving with fresh whipped cream or ice cream. Enjoy!