Damson Plum Pinwheels

Whisk together flour, salt, and cardamom in a bowl. Beat together butter, cream cheese, and granulated sugar in a large bowl with an electric mixer at medium-high speed until fluffy, about 3 minutes, then beat in yolk and vanilla. Reduce speed to low and add flour mixture in 3 batches, mixing until dough just comes together. Quarter dough and flatten each piece into a block, then chill, wrapped in plastic wrap, until firm, 2 to 3 hours. Put oven rack in middle position and preheat oven to 350 °F. Line 2 large baking sheets with parchment paper. Keeping remaining 3 pieces chilled, roll out 1 piece of dough 3/4 inch thick on a lightly floured surface with a lightly floured rolling pin, then trim edges to make a 12- by 8-inch rectangle. Chill scraps, wrapped in plastic wrap. Cut rectangle into 2-inch squares with pastry wheel.