In a medium bowl stir together the 2 cups flour and the 1/3 cup sugar. Using a pastry blender, cut butter into flour mixture until pieces are pea size. In a small bowl stir together egg yolks, sour cream, and ice water. Gradually stir egg yolk mixture into flour mixture. Using your fingers, gently knead the dough just until a ball forms. Cover dough with plastic wrap; chill about 1 hour or until dough is easy to handle.
Divide dough into 8 portions. Place on lightly floured pieces of parchment. Roll dough into 6- to 7-inch circles. Transfer, on parchment, to baking sheets.
Preheat oven to 375F. Divide dough into 8 portions. On lightly floured pieces of parchment paper, roll dough portions into 6- to 7-inch circles. Transfer circles, on parchment, to baking sheets.
In a small bowl stir together the 2/3 cup sugar and 1/4 cup flour. Sprinkle a scant 2 tablespoons of the sugar mixture on each pastry circle to within 1/2 inch of the edges. In a large bowl combine fruit and the 1/4 to 1/3 cup sugar; toss gently to coat.
Spoon 3/4 to 1 cup of the fruit mixture into the center of each dough circle. Fold pastry edges over the edges of fruit. Bake tarts for 20 to 25 minutes or until fruit is tender and pastry is golden brown. If desired, dust pastry edges with powdered sugar. Makes 8 tarts.