Make the pate sucree: Pulse flour, sugar, and salt in a food processor to combine. Add butter; process until mixture resembles coarse meal, about 10 seconds. add egg yolk, and pulse. With machine running, add ice water in a slow, steady stream through feed tube until dough just holds together. Turn out dough onto a work surface; shape into a disk. Wrap in plastic, and refrigerate at least 1 hour (up to 2 days).
Make the streusel: Sift together sugar, flour, baking powder, and salt in a medium bowl. Using your hands or a pastry blender, cut in butter until mixture resembles coarse crumbs. Set aside.
On a lightly floured surface, roll out dough to about 1/8 inch thick. Fit into a 9 1/2- or 10-inch pie plate (about 1 1/2 inches deep). Trim edge to 1 inch; fold under, and crimp as desired. Pierce bottom of dough all over with a fork. Transfer to freezer for 30 minutes.
Preheat oven to 400 degrees. Cover edge of crust with foil. Line crust with parchment paper, and fill with pie weights or dried beans. Bake, covered, 10 minutes. Remove weights and parchment (keep foil on edge). Bake until pale golden brown, 5 to 8 minutes more. Transfer to a wire rack to cool slightly; remove foil; reduce oven temperature to 375 degrees.
Make the filling: Put peaches into a medium bowl, and sprinkle with sugar and salt; gently toss to coat. let stand 15 minutes. Spread 2 tablespoons creme fraiche onto bottom of crust; sprinkle with one-third of the streusel. Arrange peaches on top; spread or dot with remaining 3 tablespoons creme fraiche. Sprinkle with remaining streusel.
Bake pie until creme fraiche is bubbling and streusel is golden brown, about 50 minutes. Cover edge of crust with foil if it's browning too quickly. Let cool on a wire rack 15 minutes. Serve warm or at room temperature.