Pastry: In your food processor, place the flour, salt, and sugar and process until combined. Add the butter and process until the mixture resembles coarse meal (about 15 seconds). In a small bowl, whisk the egg and vanilla. Then gradually pour in a steady stream, with the motor running, through the feed tube until the pastry just holds together when pinched. Add water, if necessary. Do not process more than about 30 seconds.

Transfer the pastry to an 11 inch (28 cm) fluted tart pan, and press evenly over the bottom and up the sides of the pan. Cover and place in the refrigerator while you prepare the blueberry topping.

Preheat the oven to 425 degree F (220 degree C).

In a large bowl combine the sugar and flour. Add 2 1/2 cups of fresh blueberries and toss to coat. Remove the chilled pastry from the refrigerator and evenly pour in the blueberries and sugar/flour mixture. Place the tart pan on a large baking sheet and bake for 15 minutes. Reduce the oven temperature to 350 degrees F (180 degrees C) and continue to bake until the pastry is golden brown (about 30 - 35 minutes). (Halfway through the baking time, stir the berries if there is any flour on them.) Remove from oven and place on a wire rack. Top with the remaining 2 1/2 cups of blueberries (crown side up), pressing them gently into the hot blueberry jam. I like to make concentric circles with the blueberries, starting at the outside edge. Let the tart cool to room temperature before serving. Dust with powdered sugar and serve with softly whipped cream or ice cream. Cover and store leftovers in the refrigerator.

Makes one - 11 inch (28 cm) tart.