1Heat oven to 350 degrees. In a food processor, combine flour, sugar, and cinnamon; process for 10 seconds. Add butter and process until mixture resembles coarse meal, 15 to 20 seconds.
2Combine egg yolk with 2 tablespoons ice water and add to flour mixture. Process until the dough comes together, about 7 seconds. Transfer to a clean work surface and compress into a flattened circle.
3Lightly dust the work surface with flour; roll out dough to just thinner than 1/4 inch. Using a round or square cookie cutter, cut out shapes and press into 2- to 3-inch tartlet tins or a small muffin-top pan. Shape crust as desired, fill each with 1 1/2 to 2 teaspoons jam, and decorate tops with cutouts of dough. At this point, the tarts can be refrigerated for several hours.
4Bake until golden brown, 20 to 25 minutes. Transfer tarts from tins to a wire rack to cool.