8 tablespoons (1 stick) cold unsalted butter, cut up
3/4 cup (4 1/2 ounces) finely cut moist prunes
Heat oven to 375 degrees F. Put flour, baking powder, baking soda, cardamom, and salt into a large bowl; mix well.
In another bowl, beat yogurt, egg, sugar, and lemon peel until well blended.
Add butter to the flour mixture and cut in with a pastry blender or rub in with your fingers, until the mixture looks like fine granules. Add prunes and toss to distribute evenly.
Add yogurt mixture and stir with a spoon until a sticky dough forms. Drop 1/3 cupfuls of dough 2 inches apart on an ungreased cookie sheet. Bake 20 to 25 minutes, until golden brown. Cool, loosely covered with a dishtowel, on a wire rack.