Lightly butter a 9-inch springform pan. Line a baking sheet with parchment paper. Set aside.
For the cake, cream the sugar with the butter until fluffy. Add in the egg yolks and egg, the remaining ingredients to make a soft dough. Press into a mound and wrap In wax paper and refrigerate one hour or overnight.
For the pastry cream, in a 3-quart saucepan, heat the milk and egg yolks; over gently heat, until simmering. Mix the sugar, flour and salt together in a small bowl. Once milk is simmering (almost boiling) whisk in the dry mixture and whisk over low heat until it thickens. You want to cook this over gentle heat so as not to cook the egg yolks too fast.
Remove from stove and cool to just warm, and then stir in vanilla.
Refrigerate pastry cream.
Preheat oven to 350 F. For baking the cake, divide dough into two parts - with a slightly larger portion as the bottom of the cake. Press it into the cake pan, covering the bottom and partially up the sides.
Spoon the pastry cream on the bottom dough. With the remaining dough, roll out (between floured wax paper if that is easier) on a floured board. Place this dough portion over the pastry filling - arranging it as evenly as you can to cover it.
Place the cake on the prepared baking sheet. Bake until done, about 40 minutes, until golden brown on top.
Garnish with a dusting of confectioners’ sugar.
Refrigerate overnight before serving.
To make the Sour Cherry Sauce, drain the cherries and set aside. Remove 1/3 cup juice and mix with cornstarch. Put the remaining juice in a small saucepan and bring to a boil with the sugar. Add in the cornstarch mixture and simmer, allowing mixture to thicken. Remove from stove and stir in the cherries. Refrigerate and offer with chilled cake on the side.