Combine flour and salt in a medium-size bowl. With a pastry blender or two knives, cut in the butter until crumbly. Dissolve the baking soda in the water. Gradually add to the flour. Combine until dough forms (more water may be required to make a firm dough). Form dough into a ball, flatten slightly, and roll out onto a lightly floured board with a floured rolling pin. Transfer to a 9-inch pie plate, trim the edges and flute. Cover with plastic wrap and refrigerate until ready to use.
Preheat oven to 350°F. Beat eggs until frothy. Beat in the sugar, cream and currant jelly until well combined. Stir in the zest of 1 lemon and lemon juice. Pour the filling carefully into the pie shell and bake for 30 to 35 minutes, or until the custard is set and the pastry is golden brown. Let cool on a rack. Decorate with fresh raspberries, strawberries, or candied violets.