Sift flour, baking powder and salt. Beat 1/2 cup sugar with shortening until light and creamy. Add lemon rind, then eggs, one at a time; beat well. Add flour in fourths, beating after each addition. Spread half of batter in greased 8x8 inch pan. Top with peaches. Mix 1/3 cup sugar, cinnamon and nuts; sprinkle over all. Bake 50 minutes at 350 degrees. Serve warm, cut into squares and top with whipped cream, if desired.