In a small bowl combine raisins and rum. Set aside to soak; do not drain.
In a large mixing bowl beat egg yolks, 2 tablespoons granulated sugar, vanilla, and salt with an electric mixer until thick and lemon-colored. Add flour and milk alternately to yolk mixture, beating on low speed after each addition until batter is smooth. Stir in the undrained raisin mixture and melted margarine or butter.
Wash beaters thoroughly. In a small mixing bowl beat egg whites with an electric mixer on medium to high speed until soft peaks form (tips curl). Gradually add 2 tablespoons granulated sugar, beating on high speed until stiff peaks form (tips stand straight). Gently fold beaten egg whites into egg yolk mixture, leaving a few puffs of egg white. Do not overbeat.
Generously grease a 10-inch ovenproof skillet. Pour batter into the skillet. Immediately place skillet in a 400 degree F oven. Bake about 15 minutes or until pancake is golden brown. Let cool in pan 10 minutes. Invert pancake onto serving platter. Sprinkle generously with powdered sugar. Cut into pieces. If desired, serve with applesauce or jam. Makes 8 servings.