Beat together the egg, sugar and 1 to 2 tablespoons of warm water until light and creamy. Gradually fold in the flour until the mixture leaves the sides of the bowl clean. For the filling, beat together the eggs and sugar until creamy. Fold in the lemon rind, ground almonds and cinnamon. Roll out the pastry to 1/8-inch thick on a floured work surface. Line a greased, loose-bottomed 10-inch tart pan with the pastry. Prick it all over with a fork and spoon the filling on top. Bake in a preheated oven at 355 degrees F for about 30 minutes, until golden brown. Leave the almond tart to cool in the pan. Once cool, transfer it to a serving plate and sprinkle with confectioners' sugar before serving. A St. James' cross template can be used, if liked.