In a small bowl, add egg and 1 tablespoon ofwater and whisk well. Set aside.
In food processor, place flour and 1tablespoon of sugar and pulse until combined.
While motor is running, slowly add butter,one tablespoon at a time and pulse until well combined.
Now slowly add egg mixture and pulse untildough ball forms.
Dust a smooth surface with extra flour.
Place the dough ball onto a floured surfaceand with your hands, knead until smooth.
Shape the dough into a ball and cover withplastic wrap.
Refrigerate the dough for about 15 minutes.
Arrange a rack in the lowest position ofoven.
Preheat your oven to 475 °F.
Unwrap the dough and place onto a flouredsurface.
With a lightly floured rolling pin, roll thedough into a circle that will in a 9x11-inch tart pan.
Arrange the dough into the tart pan.
With your hands, press the dough firmly intothe bottom and up the sides of the pan.
Then trim any excess dough from the edges.
With a fork, poke the holes in the crust atmany places.
Sprinkle the top of crust with cornstarch andremaining sugar evenly.
Then arrange the apricots halves over thecrust.
Bake for about 10 minutes.
After 10 minutes of baking, set thetemperature of oven to 425 °F and bake for about 30 minutes.
Remove the tart pan from oven and place ontoa wire rack to cool.
In a small bowl, blend together the apricotjam and remaining water.
Brush the top of tart with jam mixture.
Cut into desired-sized slices and serve.