In the bowl of a food processor, combine flour, sugar, cornmeal, and salt. Pulse to combine. Add butter, tossing with a wooden spoon to coat butter cubes in flour mixture; then pulse several times until mixture resembles coarse oatmeal. Add egg yolk and 2 tablespoons milk, cream, or water; pulse until dough begins to come together in a ball. (Add an extra tablespoon of liquid if you need it to bring the dough together.)
Transfer dough to a lightly floured work surface and knead briefly; then shape it into a disk about 5 inches across. Wrap in plastic and refrigerate at least 1 hour, or overnight.
Using a lightly floured rolling pin, roll out dough into a shape about ½ inch wider than the 8-inch tart pan you’re using. Fold dough loosely in half (so that it doesn’t sag) and transfer it to the pan; line the pan with it, being careful not to stretch the dough. Trim any excess dough from the rim of the pan, leaving a blunt, neat edge. Gather the trimmings into a ball (about the size of a table-tennis ball).
Wrap the tart and the small ball of dough in plastic and refrigerate 1 hour, or up to 2 days.
When you’re ready to bake, heat oven to 375°. Remove tart pan from refrigerator and spread fruit preserves evenly over crust. Grate chilled pastry ball over preserves; then sprinkle almonds on top. Bake on a rack in the center of the oven until pastry is golden, filling is bubbly, and almonds are toasted, about 40 to 50 minutes. Transfer to a wire rack to cool. When tart is completely cool, dust with confectioners’ sugar. Serve at room temperature.