Preheat oven to 375 degree F. In a 10-inch ovenproof skillet melt the 1/2 cup butter over medium heat. Stir in the quince or apples and 2/3 cup sugar. Cook over medium heat, stirring occasionally, until bubbly. Reduce heat to medium-low. Cook, uncovered, for 20 minutes more or until quince or apples are very tender, stirring occasionally (if using quince, mixture will thicken and turn deep golden brown). Remove from heat.
Meanwhile, in a medium mixing a bowl stir together all-purpose flour and 3 tablespoons sugar. Cut in 1/2 cup butter until pieces are pea-size. Using a fork, stir in egg and 1 to 2 tablespoons cold water until all dough is moistened. Form into ball.
On a lightly floured surface, use your hands to slightly flatten dough. Roll dough from center to edge into a 10-inch circle. Cut slits in the pastry. Unroll pastry over quince mixture in skillet, being careful not to stretch pastry. If necessary, carefully fold under edges of pastry.
Bake about 30 minutes or until the pastry is golden brown and filling is bubbly. Cool in skillet on a wire rack for 5 minutes. Invert onto a large serving plate. Carefully lift off the skillet. Allow to stand about 20 minutes more. Makes 12 servings.