Preheat oven to 350°F (175°C). Grease and flour 5 (8-inch) round pans.

Grind the blanched almonds in a food processor with 1/4 cup confectioners' sugar. Cream the butter with the remaining 3/4 cup confectioners' sugar until light and fluffy. Beat in the egg. Stir in the almond extract, salt, and ground almond mixture. Add the flour and mix thoroughly. Divide the dough into 5 equal parts. Roll each piece between 2 sheets of waxed paper or parchment paper to fit the pans, or pat each piece of dough into the prepared pans.

Bake in the preheated oven until the edges begin to brown, about 20 minutes. Remove from the pans while still hot.

To make the Prune Filling: Place the prunes in a saucepan with the water. Bring to a boil, remove from heat and let stand for 10 minutes. Drain and reserve the liquid. Puree the prunes in a food processor.

Return the prune puree to the saucepan and add the white sugar, cinnamon, lemon juice, and 4 tablespoons reserved prune liquid. Bring the mixture to a boil, then remove from heat.