Cherries dotted throughout a puddinglike filling give these tarts a juicy bite.
Make the crusts: Beat butter and confectioners' sugar with a mixer on medium speed until smooth. Add yolk, and mix until combined. Add flour and 1/2 teaspoon coarse salt; mix until just combined. Press dough into a disk, and wrap in plastic. Refrigerate for at least 1 hour or up to 3 days.
Set six 4-inch tart rings on a parchment-lined baking sheet. Roll out dough to 1/8-inch thickness on a lightly floured surface. Cut out six 5 1/2-inch circles, rerolling scraps as needed. Press dough into bottoms and up sides of tart rings, patching any holes or tears. Trim excess dough flush with edges of rings using a knife. Prick bottoms of tart shells all over with a fork, and refrigerate until firm, about 1 hour. Meanwhile, preheat oven to 325 degrees.
Bake until pale gold, pressing down dough if puffing, about 20 minutes. Let cool.
Make the filling: Raise oven temperature to 375 degrees. Gently whisk together eggs, creme fraiche, granulated sugar, vanilla, and a pinch of table salt. Divide mixture evenly among tart shells, and carefully drop cherry halves, cut sides down, into each. Transfer to oven, and bake until just set, 17 to 19 minutes. Let cool.
Make ahead: Dough can be frozen for up to 1 month. Thaw before using.