Positin rack in center of oven and preheat to 160ºC . Grease and flour 10x4 in tube pan. Using electric mixer, cream butter with 1.75 cups sugar in large bowl until fluffy. Gradually beat in 3 egg yolks, 2 whole eggs, water and vanilla. combine flour and baking powder in small bowl. Gradually mix dry ingredients into butter mixture (batter will be very thick). Using clean, dry beaters, beat egg whites with salt in medium bowl until soft peaks form. Add remaining 1 tablespoon sugar and beat until stiff but not dry. Fold egg whites into batter. Pour batter into prepared pan. Press coin into cake. Sprinkle with nuts and sesame seeds. Bake until toothpick inserted near center of cake comes out clean, about 1 hour 10 minutes. Cool completely in pan on rack. Run knife around pan to loosen. Invert onto plate. (Can be prepared 1 day ahead. Wrap tightly and store at room temperature).