Caramelize 1/2 cup sugar in 9-inch (about 3 1/2- to 4-inches deep) heart-shaped or round pan. Beat together 3 egg yolks, eggs, 1/2 cup sugar, evaporated milk, orange peel and 2 tablespoons rum. Set aside. To make cake batter, sift flour with 1/4 cup sugar, baking powder and salt. Place in small bowl and make well in center. Place 2 yolks, oil, 1 tablespoon rum and orange juice in well. Stir until blended, starting from center. Beat egg whites with cream of tartar until foamy. Gradually add remaining 1/4 cup sugar, beating until stiff but not dry. Gently fold batter into whites. Pour custard mixture into caramel-lined pan. Gently spoon cake batter over flan mixture. Place pan in larger pan and pour hot (not boiling) water into larger pan until it reaches half depth of cake pan. Bake at 325F 50 to 60 minutes, or until cake is done. Cool on rack or chill until ready to serve. Invert onto serving platter and pipe whipped cream rosettes around edges of flan. (C) 1992 The Los Angeles Times