Prepare the Crust: In a large bowl, whisk together flour and salt. Cut in the cold butter using a pastry blender or your fingertips until the mixture resembles coarse crumbs with some pea-sized pieces of butter remaining. Gradually add ice water, one tablespoon at a time, mixing until the dough just comes together. Form into a disc, wrap in plastic, and chill for at least 30 minutes.

Preheat Oven and Roll Dough: Preheat your oven to 400°F (200°C). On a lightly floured surface, roll the chilled dough into a 12-inch circle. Carefully transfer the dough to a standard 9-inch pie plate. Trim and crimp the edges. Line the crust with parchment paper and fill with pie weights or dried beans.

Blind Bake the Crust: Bake the crust for 15 minutes. Remove the weights and parchment paper, then bake for another 5 minutes until the bottom is set. Reduce the oven temperature to 375°F (190°C) and allow the crust to cool slightly while preparing the filling.

Prepare the Filling: In a large bowl, gently toss the sliced nectarines with the lemon juice. In a separate medium bowl, whisk together the sugar and cornstarch. Then, whisk in the lightly beaten eggs, heavy cream, and vanilla bean paste until smooth. Carefully fold in the sliced nectarines, ensuring they are evenly coated.

Assemble and Bake: Arrange the coated nectarine slices evenly within the partially baked pie shell. Pour the remaining custard mixture over the fruit. Dot the top with the small pieces of butter and sprinkle lightly with cinnamon, if using.

Bake for 40–45 minutes, or until the custard is mostly set but still has a slight jiggle in the center. If the crust begins to brown too quickly, cover the edges with foil. Let the pie cool completely on a wire rack (at least 3 hours) before slicing and serving to allow the custard to fully set.