Preheat the oven to 400* F. Roll out the pie dough until it's 1/8 inch thick. Place in the fridge while you prepare the remaining ingredients.
In a medium bowl, fold the nectarines with the brown sugar, flour, cinnamon, cardamom, lemon juice, and salt. Set aside.
In a small bowl, stir together the mascarpone, egg, sugar, lemon zest, and vanilla extract. (It will be a bit runny and there may be a few small lumps, that's ok!) Place the mascarpone filling in the center of your pie dough, leaving a two-inch rim. (It may spill over the two-inch mark, that's also ok!)
Place the nectarine filling in the center of the pie dough on top of the mascarpone filling, leaving a two-inch rim on all sides. Fold the rim over the nectarines, ensuring the filling stays inside.
Brush the crust with the egg wash, and sprinkle with turbinado sugar or almonds. Bake for 45-60 minutes or until the crust is browned and the filling is bubbly. Let cool to room-temperature and serve with vanilla ice cream!