Preheat the oven to 450 degrees F.
Sift the flour, and then add the baking powder, sugar and salt and sift again. In a large mixing bowl, cut in the butter or shortening. Add the egg, egg yolk and cream all at once and stir until all the flour is dampened. Mix in the dried cherries and lemon zest. Then stir vigorously until the mixture forms a soft dough and follows a spoon around the bowl. Turn out immediately onto a slightly floured board and knead 30 seconds. Using a rolling pin, roll out until the dough is about 1/2-inch thick, and then cut into triangles. Place on an ungreased baking sheet. Brush the tops lightly with the egg white, and sprinkle with some sugar. Bake for 12 to 15 minutes.