Sift flour and baking powder in bowl. Set aside. Use mixer to cream butter and 0.75 cup sugar. Add egg yolks, 1 at time, until mixture is satiny. Add melted chocolate, cocoa, vanilla, rum and water. Mix well. Add flour mixture. Mix well. In large, grease-free mixing bowl, beat egg whites on low speed until frothy (easiest to do with stand mixer). Add cream of tartar and salt. Beat until they hold soft peaks. Slowly add remaining sugar by tb. Do not overbeat. Peaks should still be soft. Stir quarter whites into batter. Gently fold in remaining whites. Transfer batter to generously greased (9-inch) springform pan, bottom lined with greased parchment or wax paper. Smooth surface. Bake at 180ºC until well browned and crusty and wooden pick inserted into center comes out without batter (it is not bone dry), about 35 minutes. Cool in pan on cooling rack until completely cooled. Cake will deflate as cools. Use sharp flexible knife to carefully separate cake from collar, then from bottom of spring form. Place piece of plastic wrap over cake and gently compress high edges of cake to make uniform surface. Invert cake onto serving platter. Remove paper. GLAZEHeat raspberry preserves until flowing. Brush onto top and sides of cake. Combine water, butter and chocolate in microwaveable dish or small pot. Gently melt chocolate. Add powdered sugar and rum. Stir well. Let glaze stand until slightly thickened and spreadable. Use flexible spreader to coat sides and top of cake with glaze. Can be made day ahead and held at room temperature, covered airtight. Serve with raspberries, passed separately in bowl. ----