Step 1Place butter, egg yolk, salt and water in bowl of food processor. Pulse until butter is slightly creamed, about 6 times. Add flour and powdered sugar. Process until just uniformly moist and starting to form clumps; do not let form ball. Transfer to plastic bag; working through bag, compress dough into ball, then flatten into 8-inch-diameter disk. Refrigerate until firm, about 2 hours or freeze about 20 minutes. (Can also be frozen up to 1 month; thaw in refrigerator before rolling.)
Step 2Roll dough on lightly floured surface to circle about 1/8-inch thick. Center dough over greased 11-inch tart pan with removable bottom and press into place. Use kitchen shears to trim dough, leaving 1-inch overlap beyond pan's edge. Fold overlap inside to form double thickness on sides. Press firmly into place, pushing overlap 1/4 inch above edge of pan (to allow for shrinkage in baking). Pinch crust to form decorative edge. Prick bottom and sides with fork. Refrigerate crust until firm, at least 30 minutes. Line crust with parchment paper and fill with uncooked beans or rice.
Step 3Bake at 400 degrees until lightly browned, 6 to 8 minutes. (If there are any cracks in crust, repair them with scraps of leftover raw dough.) Remove dried beans or rice and set pastry on cooling rack.
Step 1Beat eggs, sugar and zest until well mixed. Add orange and lemon juices and cream. Mix until smooth, 1 minute.
Step 2Carefully ladle filling into Pastry Shell. Bake at 375 degrees 10 minutes, then decrease temperature to 350 degrees. Bake until filling jiggles only slightly when pan is shaken, about 12 to 14 minutes more. Remove from oven.
Step 3Press powdered sugar through fine sieve over surface of tart. Blot lemon segments with paper towels and arrange in radial design around center.
Step 4Broil tart about 5 inches from heat source, watching constantly, until sugar begins to caramelize, 30 seconds to 1 minute. Rotate tart to brown evenly. (Tart is best served same day at room temperature; do not refrigerate before serving.) Let cool, then cut into wedges and serve.