Preheat oven to 400° F. Sift flour, baking powder, salt and 2 tablespoons of the sugar together. Work in butter until mixture crumbles. Pile into an ungreased square pan and pat even layer over bottom and halfway up the sides of the pan. Place peach slices over pastry, sprinkle mixture of cinnamon and remaining sugar over the top and bake for 12 minutes. Mix egg yolks with heavy or sour cream, and pour over top of partially cooked kuchen. Place back in oven for 30 to 40 more minutes until top is bubbly. Serve Warm.