How to Make It
Preheat oven to 350°F. Sift flour, 1/2 cup sugar, cornmeal, baking powder, and salt into bowl of a stand mixer fitted with the paddle attachment. Add butter, and beat on medium speed until ingredients are mostly incorporated, about 1 minute. Add egg, and beat on medium-high speed until ingredients are completely incorporated and dough starts to form a ball, about 30 seconds.
Transfer dough to a work surface, and gather into a ball. Press about 1 1/4 cups of the dough into a lightly greased 9- to 10-inch tart pan with removable bottom, pressing evenly onto bottom and up fluted sides. (Use a straight-sided measuring cup or a small straight rolling pin lightly coated with cooking spray to make a smooth and even surface on bottom.) Wrap remaining dough in plastic wrap, and chill with dough in pan 15 minutes. Arrange apricots, cut sides up, on chilled tart dough in bottom of pan, pressing slightly. Unwrap remaining dough; divide into 8 portions. Shape each dough portion into a ball (about 1 1/2 teaspoons each), and arrange dough balls over apricots in pan. Sprinkle with remaining 2 tablespoons sugar.
Bake in preheated oven until golden and dough is crisp, about 35 minutes. Transfer tart to a wire rack, and let cool 30 minutes.
Meanwhile, beat cream in a stand mixer fitted with the whisk attachment on medium-high speed until soft peaks form, about 1 minute. Add labneh and powdered sugar, and beat until just combined, about 10 seconds.
Remove pan rim from tart, and cut into slices. Serve with labneh whipped cream.