To make the pastry: Cream butter and icing sugar until light and fluffy. Add egg yolk, salt and water and continue to beat until combined. Stir in flour to mix until a dough is formed. Take out the dough and chill it in the refrigerator for 30 40 minutes.
Roll out the pastry to fit a tart pan. Trim the edges and leave aside to rest in the refrigerator for 30 minutes before baking blind, covered with foil.
Bake in a preheated oven at 170°c for 20 minutes. Remove and leave aside to cool.
For the filling, combine almonds, sugar and corn flour together in a mixing bowl. Add the butter and beat with hand-held electric beater.
Whisk in the egg and add the vanilla essence. Spread the filling over the half-baked crust dough.
Arrange the plums atop the filling. Brush over with some melted butter.
Bake in a preheated oven at 180°c for 35 minutes or until the plums turn soft and the filling is golden in colour. Brush apricot gel glaze over the tart.